Methods of determining catheter orientation

ABSTRACT

Systems, devices and methods of determining orientation of a distal end of a medical instrument (e.g., electrode-tissue orientation of an RF ablation catheter) are described herein. One or more processors may be configured to receive temperature measurements from each of a plurality of temperature-measurement devices distributed along a length of the distal end of the medical instrument and determine the orientation from a group of two or more possible orientation options based on whether temperature measurement values or characteristics of temperature response determined from the temperature measurement values satisfy one or more orientation criteria.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/782,714, filed Oct. 12, 2017, which is a continuation ofInternational PCT Application No. PCT/US2017/022264, filed Mar. 14,2017, which claims priority to U.S. Provisional Application No.62/308,461, filed Mar. 15, 2016, to U.S. Provisional Application No.62/315,661, filed Mar. 30, 2016, to U.S. Provisional Application No.62/323,502, filed Apr. 15, 2016, and to U.S. Provisional Application No.62/418,057, filed Nov. 4, 2016, the entire contents of each of which areincorporated herein by reference in their entirety.

BACKGROUND

Tissue ablation may be used to treat a variety of clinical disorders.For example, tissue ablation may be used to treat cardiac arrhythmias byat least partially destroying (e.g., at least partially or completelyablating, interrupting, inhibiting, terminating conduction of, otherwiseaffecting, etc.) aberrant pathways that would otherwise conduct abnormalelectrical signals to the heart muscle. Several ablation techniques havebeen developed, including cryoablation, microwave ablation, radiofrequency (RF) ablation, and high frequency ultrasound ablation. Forcardiac applications, such techniques are typically performed by aclinician who introduces a catheter having an ablative tip to theendocardium via the venous vasculature, positions the ablative tipadjacent to what the clinician believes to be an appropriate region ofthe endocardium based on tactile feedback, mapping electrocardiogram(ECG) signals, anatomy, and/or fluoroscopic imaging, actuates flow of anirrigant to cool the surface of the selected region, and then actuatesthe ablative tip for a period of time and at a power believed sufficientto destroy tissue in the selected region. In ablation proceduresinvolving radiofrequency energy delivery using one or more electrodes,the clinician strives to establish stable and uniform contact betweenthe electrode(s) and the tissue to be ablated.

Successful electrophysiology procedures require precise knowledge aboutthe anatomic substrate. Additionally, ablation procedures may beevaluated within a short period of time after their completion. Cardiacablation catheters typically carry only regular mapping electrodes.Cardiac ablation catheters may incorporate high-resolution mappingelectrodes. Such high-resolution mapping electrodes provide moreaccurate and more detailed information about the anatomic substrate andabout the outcome of ablation procedures. High-resolution mappingelectrodes can allow the electrophysiology to evaluate precisely themorphology of electrograms, their amplitude and width and to determinechanges in pacing thresholds. Morphology, amplitude and pacing thresholdare accepted and reliable electrophysiology (EP) markers that provideuseful information about the outcome of ablation.

SUMMARY

According to some embodiments, an ablation device comprises an elongatebody comprising a distal end, an electrode positioned at the distal endof the elongate body, at least one thermal shunt member placing a heatabsorption element in thermal communication with the electrode toselectively remove heat from at least one of the electrode and tissuebeing treated by the electrode when the electrode is activated, whereinthe at least one thermal shunt member extends through an interior of theelectrode to dissipate and remove heat from the electrode during use,and wherein the at least one thermal shunt member comprises at least onelayer or coating such that the at least one thermal shunt member doesnot extend to an exterior of the elongate body, and at least one fluidconduit extending at least partially through an interior of the elongatebody and at least partially through an interior of the at least onethermal shunt member, wherein the at least one thermal shunt member isin thermal communication with the at least one fluid conduit, the atleast one fluid conduit being configured to place the electrode in fluidcommunication with a fluid source to selectively remove heat from theelectrode or tissue.

According to some embodiments, the at least one thermal shunt membercomprises a thermal diffusivity greater than 1.5 cm²/sec, wherein theelectrode comprises a composite electrode, wherein the compositeelectrode comprises a first electrode portion and at least a secondelectrode portion, wherein an electrically insulating gap is locatedbetween the first electrode portion and the at least a second electrodeportion to facilitate high-resolution mapping along a targetedanatomical area, and wherein the at least one fluid conduit comprises atleast one opening.

According to some embodiments, an ablation device comprises an elongatebody (e.g., catheter, other medical instrument, etc.) comprising adistal end, an ablation member positioned at the distal end of theelongate body, at least one thermal shunt member placing a heat shuntingelement in thermal communication with the ablation member to selectivelyremove heat from at least a portion of the ablation member or tissuebeing treated by the ablation member when the ablation member isactivated, wherein the heat shunting element of the at least one thermalshunt extends at least partially through an interior of the ablationmember to help remove and dissipate heat generated by the ablationmember during use, at least one layer or coating positioned at leastpartially along an outer surface of the at least one thermal shuntmember, and at least one fluid conduit extending at least partiallythrough an interior of the elongate body, wherein the at least onethermal shunt member is in thermal communication with the at least onefluid conduit.

According to some embodiments, the at least one layer or coating iselectrically insulative, the at least one fluid conduit extends at leastpartially through an interior of the at least one thermal shunt member;wherein the at least one fluid conduit comprises at least one opening,and wherein the at least one thermal shunt member comprises a thermaldiffusivity greater than 1.5 cm²/sec.

According to some embodiments, a method of heat removal from an ablationmember during a tissue treatment procedure comprises activating anablation system, the system comprising an elongate body comprising adistal end, an ablation member positioned at the distal end of theelongate body, wherein the elongate body of the ablation systemcomprises at least one thermal shunt member along its distal end,wherein the at least one thermal shunt member extends at least partiallythrough an interior of the ablation member, wherein at least one layeror coating is positioned at least partially along an outer surface ofthe at least one thermal shunt member, at least partially removing heatgenerated by the ablation member along the distal end of the elongatebody via the at least one thermal shunt member so as to reduce thelikelihood of localized hot spots along the distal end of the elongatebody, wherein the elongate body further comprises at least one fluidconduit or passage extending at least partially through an interior ofthe elongate body, and delivering fluid through the at least one fluidconduit or passage to selectively remove heat away from the ablationmember when the ablation member is activated.

According to some embodiments, the at least one layer or coating iselectrically insulative. In some embodiments, the at least one layer orcoating comprises an electrical resistivity of greater than 1000 Ωcm at20° C. In some embodiments, the at least one layer or coating isthermally insulative. In some embodiments, the at least one layer orcoating comprises a thermal conductivity of less than 0.001 W/(cm K) at20° C. In some arrangements, the at least one layer or coating comprisesa polymeric material (e.g., thermoset polymers, polyimide, PEEK,polyester, polyethylene, polyurethane, pebax, nylon, hydratable polymersand/or the like). In some embodiments, the at least one layer or coatingcomprises a thickness between 1 and 50 μm. In some embodiments, the atleast one layer or coating comprises a thickness less than 100 μm. Insome arrangements, the at least one layer or coating comprises a singlelayer or coating. In other embodiments, the at least one layer orcoating comprises more than one layer or coating. In some embodiments,the at least one layer or coating is directly positioned along a surfaceof the at least one shunt member. In some embodiments, the at least onelayer or coating is not directly positioned along a surface of the atleast one shunt member. In some embodiments, at least one intermediatemember or structure is positioned between the at least one shunt memberand the at least one layer or coating. In some embodiments, the at leastone layer or coating is secured to the at least one heat shunt memberusing an adhesive. In some embodiments, the at least one layer orcoating is secured to the at least one heat shunt member using a pressfit connection, dip molding or other molding technology.

According to some embodiments, the at least one thermal shunt membercomprises a thermal diffusivity greater than 1.5 cm²/sec. In someembodiments, the at least one thermal shunt member comprises a diamond(e.g., an industrial diamond). In some embodiments, the at least onethermal shunt member comprises Graphene or another carbon-basedmaterial.

According to some embodiments, the electrode comprises a compositeelectrode, wherein the composite electrode comprises a first electrodeportion and at least a second electrode portion, wherein an electricallyinsulating gap is located between the first electrode portion and the atleast a second electrode portion. In some embodiments, the at least onefluid conduit is in direct thermal communication with the at least onethermal shunt member. In some embodiments, the at least one fluidconduit is in indirect thermal communication with the at least onethermal shunt member. In some arrangements, the at least one fluidconduit comprises at least one opening, wherein the at least one openingplaces irrigation fluid passing through the at least one fluid conduitin direct physical contact with at least a portion of the at least onethermal shunt member.

According to some embodiments, a mapping system configured to processdata related to a targeted anatomical location being treated comprisesat least one processor, wherein the processor is configured to, uponexecution of specific instructions stored on a computer-readable medium,receive and process mapping data of the targeted anatomical location andto create a three-dimensional model of the targeted anatomical location,and at least one output device for displaying the three-dimensionalmodel of the targeted anatomical location to a user, wherein theprocessor is configured to be operatively coupled to at least onecomponent of a separate ablation system, wherein the separate ablationsystem is configured to selectively ablate at least a portion of thetargeted anatomical location, the separate ablation system comprising atleast one electrode positioned along a distal end of a catheter, the atleast one processor being configured to receive ablation data from theseparate ablation system, wherein the ablation data relate to at leastone ablation performed along a tissue of the targeted anatomicallocation, wherein the mapping system is configured to determine areal-time location of the at least one electrode relative to thethree-dimensional model of the targeted anatomical location to assist auser in ablating the tissue of the targeted anatomical location, andwherein the at least one processor is configured to generate arepresentation on the at least one output device, the representationcomprising the three-dimensional model of the targeted anatomicallocation, the real-time location of the at least one electrode and atleast a portion of the ablation data received from the separate ablationsystem.

According to some embodiments, a mapping system configured to processdata related to a targeted anatomical location being treated comprisesat least one processor, wherein the processor is configured to, uponexecution of specific instructions stored on a computer-readable medium,receive and process mapping data of the targeted anatomical location andto create a three-dimensional model of the targeted anatomical location,wherein the at least one processor is configured to be operativelycoupled to at least one output device for displaying thethree-dimensional model of the targeted anatomical location to a user,wherein the processor is configured to be operatively coupled to atleast one component of a separate ablation system, wherein the separateablation system is configured to selectively ablate at least a portionof the targeted anatomical location, the separate ablation systemcomprising at least one electrode positioned along a distal end of acatheter, the at least one processor being configured to receiveablation data from the separate ablation system, wherein the ablationdata relate to at least one ablation performed along a tissue of thetargeted anatomical location, wherein the mapping system is configuredto determine a real-time location of the at least one electrode relativeto the three-dimensional model of the targeted anatomical location toassist a user in ablating the tissue of the targeted anatomicallocation, and wherein the at least one processor is configured togenerate a representation on the at least one output device, therepresentation comprising the three-dimensional model of the targetedanatomical location, the real-time location of the at least oneelectrode and at least a portion of the ablation data received from theseparate ablation system.

According to some embodiments, the separate ablation system isintegrated into a single system with the mapping system. In someembodiments, the at least one processor of the mapping system isconfigured to be operatively coupled to at least one separate mappingsystem, wherein the at least one separate mapping system is configuredto obtain and process EGM or other electrical activity data of thetargeted anatomical location. In one embodiment, the at least oneseparate mapping system comprises multiple mapping electrodes. In someembodiments, the at least one separate mapping system is integrated withthe mapping system.

According to some embodiments, a system of any of the preceding claims,wherein the ablation data comprises one or more of the following:electrode orientation, temperature data related to tissue being treated,temperature data of one or more sensors included within the system,qualitative or quantitative contact information, impedance information,a length or a width of a lesion created by the ablation system, a volumeof a lesion created by the ablation system, a subject's heart rate data,a subject's blood pressure data, and the like.

According to some embodiments, the representation on the at least oneoutput device further comprises EGM data, rotor map data and/or otherelectrical activity data. In some embodiments, the EGM data, rotor mapdata and/or other electrical activity data is received by the at leastone processor via a separate mapping system that is operatively coupledto the mapping system.

According to some embodiments, the data in the representation on the atleast one output device is provided textually and/or graphically. Insome embodiments, at least a portion of the ablation data is displayedon the at least one output device along or near a corresponding ablationlocation.

According to some embodiments, at least a portion of the ablation datais configured to be intermittently displayed on the representation ofthe at least one output device. In some embodiments, at least a portionof the ablation data is displayed on the representation of the at leastone output device when selected by a user. In some embodiments, at leasta portion of the ablation data is configured to be displayed on therepresentation by using a selection device to select a specifictreatment location. In one embodiment, the selection device comprises amouse, a touchpad, a dial or another type of manipulatable controller.In several arrangements, the selection device comprises a touchscreen,wherein the user is able to make a selection on the touchscreen usinghis or her finger.

According to some embodiments, the system further comprises the ablationsystem (e.g., an ablation system comprising a catheter with at least onedistal electrode or other energy delivery member, a generator and/or thelike). In some embodiments, the ablation system comprises aradiofrequency ablation system.

According to some embodiments, the processor is part of the mappingsystem. In some embodiments, the processor is not part of the mappingsystem, but is operatively coupled to the mapping system. In someembodiments, the processor is part of the separate ablation system. Inone embodiment, the processor is part of a stand-alone interface unitthat is coupled to the mapping system.

According to some embodiments, a method of integrating data from anablation device with mapping data comprises generating athree-dimensional map of a targeted anatomical location using a mappingsystem, receiving ablation data from an ablation system, and displayingthe three-dimensional map and at least a portion of the ablation data ona single output device (e.g., monitor, screen, etc.).

According to some embodiments, the mapping system comprises anelectroanatomical navigation system. In some embodiments, the mappingsystem and the ablation system are integrated into a single system. Inother embodiments, the mapping system and the ablation system areseparate from each other. In some embodiments, the method additionallycomprises receiving electrical activity data from a second mappingsystem. In some embodiments, the electrical activity data comprise EGMactivity data, rotor mapping data and/or any other electrical data.

According to some embodiments, the ablation data comprises one or moreof the following: electrode orientation, temperature data related totissue being treated, temperature data of one or more sensors includedwithin the system, qualitative or quantitative contact information,impedance information, a length or a width of a lesion created by theablation system, a volume of a lesion created by the ablation system, asubject's heart rate data, a subject's blood pressure data, and thelike.

According to some embodiments, the ablation data is provided textuallyand/or graphically on the output device. In some embodiments, at least aportion of the ablation data is displayed on the output device along ornear a corresponding ablation location. In some embodiments, at least aportion of the ablation data is configured to be intermittentlydisplayed on the output device.

According to some embodiments, at least a portion of the ablation datais displayed on the output device when selected by a user. In someembodiments, at least a portion of the ablation data is configured to bedisplayed by using a selection device to select a specific treatmentlocation. In several arrangements, the selection device comprises amouse, a touchpad, a dial or another type of manipulatable controller.In some embodiments, the selection device comprises a touchscreen,wherein the user is able to make a selection on the touchscreen usinghis or her finger.

According to some embodiments, the method further comprises alerting auser of potential gaps along a targeted anatomical location. In oneembodiment, alerting a user comprises highlighting gaps on the outputdevice.

According to some embodiments, a device for ablation and high-resolutionof cardiac tissue comprises an elongate body (e.g., catheter, othermedical instrument, etc.) comprising a distal end and an electrodeassembly positioned along the distal end of the elongate body, whereinthe electrode assembly comprises a first electrode portion, at least asecond electrode portion positioned adjacent the first electrodeportion, the first electrode portion and the second electrode portionbeing configured to contact tissue of a subject and deliverradiofrequency energy sufficient to at least partially ablate thetissue, at least one electrically insulating gap positioned between thefirst electrode portion and the second electrode portion, the at leastone electrically insulating gap comprising a gap width separating thefirst and second electrode portions, and at least one separatorpositioned within the at least one electrically insulating gap, whereinthe at least one separator contacts a proximal end of the firstelectrode portion and the distal end of the second electrode portion.The device additionally comprises at least one conductor configured toelectrically couple an energy delivery module to at least one of thefirst and second electrode portions, wherein the at least one conductoris electrically coupled to an energy delivery module and wherein afrequency of energy provided to the first and second electrodes is inthe radiofrequency range.

According to some embodiments, the device further comprises a filteringelement electrically coupling the first electrode portion to the secondelectrode portion and configured to present a low impedance (e.g.,effectively shorting the two electrode portions) at a frequency used fordelivering ablative energy via the first and second electrode portions,wherein the filtering element comprises a capacitor, wherein thecapacitor comprises a capacitance of 50 to 300 nF (e.g., 100 nF, 50-100,100-150, 150-200, 200-250, 250-300 nF, values between the foregoingranges, etc.), wherein the elongate body comprises at least oneirrigation passage, said at least one irrigation passage extending tothe first electrode portion, wherein the first electrode portioncomprises at least one outlet port in fluid communication with the atleast one irrigation passage, wherein the gap width is approximately 0.2to 1.0 mm (e.g., 0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7,0.7-0.8, 0.8-0.9, 0.9-1.0 mm, values between the foregoing ranges, lessthan 0.2 mm, greater than 1 mm, etc.), wherein a series impedance oflower than about 3 ohms (Ω) (e.g., 0-1, 1-2, 2-3 ohms, values betweenthe foregoing ranges, etc.) is introduced across the first and secondelectrode portions in the operating RF frequency range, and wherein theoperating RF frequency range is 200 kHz to 10 MHz (e.g., 200-300,300-400, 400-500, 500-600, 600-700, 700-800, 800-900, 900-1000 kHz, upto 10 MHz or higher frequencies between the foregoing ranges, etc.).Electrode portions or sections can be used interchangeably withelectrodes herein.

According to some embodiments, the device further comprises a firstplurality of temperature-measurement devices positioned within separateapertures formed in a distal end of the electrode assembly, the firstplurality of temperature-measurement devices (e.g., thermocouples, othertemperature sensors, etc.) being thermally insulated from the electrodeassembly, and a second plurality of temperature-measurement devices(e.g., thermocouples, other temperature sensors, etc.) positioned withinseparate apertures located in relation to the proximal end of theelectrode assembly, the second plurality of temperature-measurementdevices being thermally insulated from the electrode assembly, whereintemperature measurements determined from the first plurality oftemperature-measurement devices and the second plurality oftemperature-measurement devices facilitate determination of orientationof the electrode assembly with respect to tissue being treated, and atleast one thermal shunt member placing a heat absorption element inthermal communication with the electrode assembly to selectively removeheat from at least one of the electrode assembly and tissue beingtreated by the electrode assembly when the electrode assembly isactivated, a contact sensing subsystem comprising a signal sourceconfigured to deliver a range of frequencies to the electrode assembly,and a processing device configured to obtain impedance measurementswhile different frequencies within the range of frequencies are beingapplied to the electrode assembly by the signal source, process theimpedance measurements obtained at the different frequencies, anddetermine whether the electrode assembly is in contact with tissue basedon said processing of the impedance measurements, wherein the elongatebody comprises at least one irrigation passage, said at least oneirrigation passage extending to the first electrode portion.

According to some embodiments, the device further comprises a firstplurality of temperature-measurement devices (e.g., thermocouples, othertemperature sensors, etc.) positioned within separate apertures formedin a distal end of the electrode assembly, the first plurality oftemperature-measurement devices being thermally insulated from theelectrode assembly, and a second plurality of temperature-measurementdevices (e.g., thermocouples, other temperature sensors, etc.)positioned within separate apertures located in relation to the proximalend of the electrode assembly, the second plurality oftemperature-measurement devices being thermally insulated from theelectrode assembly, wherein temperature measurements determined from thefirst plurality of temperature-measurement devices and the secondplurality of temperature-measurement devices facilitate determination oforientation of the electrode assembly with respect to tissue beingtreated.

According to some embodiments, the device further comprises at least onethermal shunt member placing a heat absorption element in thermalcommunication with the electrode assembly to selectively remove heatfrom at least one of the electrode assembly and tissue being treated bythe electrode assembly when the electrode assembly is activated.

According to some embodiments, the device further comprises a contactsensing subsystem comprising a signal source configured to deliver arange of frequencies to the electrode assembly, and a processing deviceconfigured to obtain impedance measurements while different frequencieswithin the range of frequencies are being applied to the electrodeassembly by the signal source, process the impedance measurementsobtained at the different frequencies, and determine whether theelectrode assembly is in contact with tissue based on said processing ofthe impedance measurements.

According to some embodiments, the filtering element comprises acapacitor. In some embodiments, the capacitor comprises a capacitance of50 to 300 nF (e.g., 100 nF, 50-100, 100-150, 150-200, 200-250, 250-300nF, values between the foregoing ranges, etc.).

According to some embodiments, the at least one thermal shunt member isin thermal communication with at least one fluid conduit (e.g., internalpassageway) extending at least partially through an interior of theelongate body, the at least one fluid conduit being configured to placethe electrode in fluid communication with a fluid source to selectivelyremove heat from the electrode assembly and/or tissue of a subjectlocated adjacent the electrode assembly.

According to some embodiments, the at least one thermal shunt membercomprises a thermal diffusivity greater than 1.5 cm²/sec. In someembodiments, the at least one thermal shunt member comprises diamond(e.g., industrial-grade diamond).

According to some embodiments, the second plurality oftemperature-measurement devices is positioned along a plane that issubstantially perpendicular to a longitudinal axis of the distal end ofthe elongate body and spaced proximal to the first plurality oftemperature-measurement devices. In some embodiments, each of thetemperature-measurement devices comprises a thermocouple, a thermistorand/or any other type of temperature sensor or temperature measuringdevice or component. In some embodiments, the first plurality oftemperature-measurement devices comprises at least three (e.g., 3, 4, 5,6, more than 6, etc.) temperature sensors, and wherein the secondplurality of temperature-measurement devices comprises at least three(e.g., 3, 4, 5, 6, more than 6, etc.) temperature sensors.

According to some embodiments, the device further comprises a means forfacilitating high-resolution mapping. In some embodiments, electricallyseparating the first and second electrode portions facilitateshigh-resolution mapping along a targeted anatomical area. In someembodiments, the device further comprises at least one separatorpositioned within the at least one electrically insulating gap. In oneembodiment, the at least one separator contacts a proximal end of thefirst electrode and the distal end of the second electrode portion.

According to some embodiments, the device further comprises at least oneconductor configured to electrically couple an energy delivery module toat least one of the first and second electrodes. In some embodiments,the at least one conductor is electrically coupled to an energy deliverymodule.

According to some embodiments, a frequency of energy provided to thefirst and second electrodes is in the radiofrequency range. In someembodiments, a series impedance introduced across the first and secondelectrodes is lower than: (i) an impedance of a conductor thatelectrically couples the electrodes to an energy delivery module, and(ii) an impedance of a tissue being treated. In some embodiments, thegap width is approximately 0.2 to 1.0 mm (e.g., 0.5 mm, 0.2-0.3,0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0 mm, valuesbetween the foregoing ranges, less than 0.2 mm, greater than 1 mm,etc.). In some embodiments, the elongate body (e.g., catheter) comprisesat least one irrigation passage, said at least one irrigation passageextending to the first electrode.

According to some embodiments, the at least a second electrode comprisesa second electrode and a third electrode portion, the second electrodeportion positioned axially between the first and third electrodeportions, wherein an electrically insulating gap separates the secondand third electrode portions. In some embodiments, gaps are includedbetween the first and second electrode portions and between the secondand third electrode portions to increase a ratio of mapped tissuesurface to ablated tissue surface. In some embodiments, the ratio isbetween 0.2 and 0.8 (e.g., 0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7,0.7-0.8, ratios between the foregoing, etc.). In some embodiments, thedevice further comprises a separator positioned within the gap betweenthe second and third electrode portions.

According to some embodiments, a device for mapping and ablating tissuecomprises an elongate body (e.g., a catheter, other medical instrument,etc.) including a proximal end and a distal end, a first electrode (orelectrode portion or section) positioned on the elongate body, at leasta second electrode (or electrode portion or section) positioned adjacentthe first electrode, the first electrode (or electrode portion orsection) and the second electrode (or electrode portion or section)being configured to contact tissue of a subject and deliverradiofrequency energy sufficient to at least partially ablate thetissue, at least one electrically insulating gap positioned between thefirst electrode (or electrode portion or section) and the secondelectrode (or electrode portion or section), the at least oneelectrically insulating gap comprising a gap width separating the firstand second electrodes (or electrode portions or sections), and afiltering element electrically coupling the first electrode (orelectrode portion or section) to the second electrode (or electrodeportion or section) and configured to present a low impedance (e.g.,effectively shorting the two electrodes, portions or sections) at afrequency used for delivering ablative energy via the first and secondelectrodes (or electrode portions or sections).

According to some embodiments, the device further comprises a means forfacilitating high-resolution mapping. In some embodiments, electricallyseparating the first and second electrodes (or electrode portions orsections) facilitates high-resolution mapping along a targetedanatomical area (e.g., cardiac tissue). In some embodiments, the devicefurther comprises at least one separator positioned within the at leastone electrically insulating gap. In one embodiment, the at least oneseparator contacts a proximal end of the first electrode (or electrodeportion or section) and the distal end of the second electrode (orelectrode portion or section). In some embodiments, the device furthercomprises at least one conductor configured to electrically couple anenergy delivery module to at least one of the first and secondelectrodes (or electrode portions or sections). In some embodiments, theat least one conductor is electrically coupled to an energy deliverymodule.

According to some embodiments, a frequency of energy provided to thefirst and second electrodes is in the radiofrequency range. In someembodiments, the filtering element comprises a capacitor. In someembodiments, the capacitor comprises a capacitance of 50 to 300 nF(e.g., 100 nF, 50-100, 100-150, 150-200, 200-250, 250-300 nF, valuesbetween the foregoing ranges, etc.). In some embodiments, the capacitorcomprises a capacitance of 100 nF. In some embodiments, a seriesimpedance of lower than about 3 ohms (Ω) (e.g., 0-1, 1-2, 2-3 ohms,values between the foregoing ranges, etc.) is introduced across thefirst and second electrodes in the operating RF frequency range. In someembodiments, the operating RF frequency range is 200 kHz to 10 MHz(e.g., 200-300, 300-400, 400-500, 500-600, 600-700, 700-800, 800-900,900-1000 kHz, up to 10 MHz or higher frequencies between the foregoingranges, etc.).

According to some embodiments, a series impedance introduced across thefirst and second electrodes is lower than: (i) an impedance of aconductor that electrically couples the electrodes to an energy deliverymodule, and (ii) an impedance of a tissue being treated. In someembodiments, the gap width is approximately 0.2 to 1.0 mm (e.g., 0.2,0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0mm, values between the foregoing ranges, less than 0.2 mm, greater than1 mm, etc.). In some embodiments, the gap width is 0.5 mm.

According to some embodiments, the elongate body comprises at least oneirrigation passage, the at least one irrigation passage extending to thefirst electrode. In some embodiments, the first electrode (or electrodeportion or section) comprises at least one outlet port in fluidcommunication with the at least one irrigation passage.

According to some embodiments, the at least a second electrode (orelectrode portion or section) comprises a second electrode (or electrodeportion or section) and a third electrode (or electrode portion orsection), the second electrode (or electrode portion or section) beingpositioned axially between the first and third electrodes (or electrodeportions or sections), wherein an electrically insulating gap separatesthe second and third electrodes (or electrode portions or sections). Insome embodiments, gaps are included between the first and secondelectrodes (or electrode portions or sections) and between the secondand third electrodes (or electrode portions or sections) to increase aratio of mapped tissue surface to ablated tissue surface. In someembodiments, the ratio is between 0.2 and 0.8 (e.g., 0.2-0.3, 0.3-0.4,0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, ratios between the foregoing, etc.).In some embodiments, the device further comprising a separatorpositioned within the gap between the second and third electrodes (orelectrode portions or sections).

According to some embodiments, an ablation device comprises a firstelectrode (or electrode portion or section) positioned at a distal endof a catheter, at least a second electrode (or electrode portion orsection) positioned at a location proximal to the first electrode (orelectrode portion or section), the first electrode (or electrode portionor section) and the second electrode (or electrode portion or section)being configured to contact tissue (e.g., cardiac tissue, other targetedanatomical tissue, etc.) of a subject and deliver energy sufficient toat least partially ablate the tissue, an electrically insulating gappositioned between the first electrode (or electrode portion or section)and the second electrode (or electrode portion or section), theelectrically insulating gap comprising a gap width separating the firstand second electrodes (or electrode portions or sections), and afiltering element electrically coupling the first electrode (orelectrode portion or section) to the second electrode (or electrodeportion or section).

According to some embodiments, electrically separating the first andsecond electrodes (or electrode portions or sections) facilitateshigh-resolution mapping along a targeted anatomical area. In someembodiments, the device further comprises at least one separatorpositioned within the at least one electrically insulating gap. Inseveral embodiments, the at least one separator contacts a proximal endof the first electrode (or electrode portion or section) and the distalend of the second electrode (or electrode portion or section).

According to some embodiments, the device additionally comprises atleast one conductor configured to energize at least one of the first andsecond electrodes (or electrode portions or sections). In oneembodiment, the at least one conductor is electrically coupled to anenergy delivery module (e.g., a RF generator).

According to some embodiments, the device further comprises means forconnectivity to an electrophysiology recorder. In some embodiments, thedevice is configured to connect to an electrophysiology recorder.

According to some embodiments, a frequency of energy provided to thefirst and second electrodes is in the radiofrequency (RF) range. In someembodiments, the operating RF frequency range is 200 kHz to 10 MHz(e.g., 200-300, 300-400, 400-500, 500-600, 600-700, 700-800, 800-900,900-1000 kHz, up to 10 MHz or higher frequencies between the foregoingranges, etc.). In some embodiments, the filtering element comprises acapacitor. In some embodiments, the capacitor comprises a capacitance of50 to 300 nF (e.g., 100 nF, 50-100, 100-150, 150-200, 200-250, 250-300nF, values between the foregoing ranges, etc.). In some embodiments, aseries impedance of less than 3 ohms (Ω) (e.g., 0-1, 1-2, 2-3 ohms,values between the foregoing ranges, etc.) is introduced across thefirst and second electrodes (or electrode portions or sections) at 500kHz.

According to some embodiments, a series impedance introduced across thefirst and second electrodes is lower than: (i) an impedance of aconductor that electrically couples the electrodes to an energy deliverymodule, and (ii) an impedance of a tissue being treated. In someembodiments, the gap width is approximately 0.2 to 1.0 mm (e.g., 0.2,0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0mm, values between the foregoing ranges, less than 0.2 mm, greater than1 mm, etc.). In one embodiment, the gap width is 0.5 mm.

According to some embodiments, the at least a second electrode (orelectrode portion or section) comprises a second electrode (or electrodeportion or section) and a third electrode (or electrode portion orsection), the second electrode (or electrode portion or section) beingpositioned axially between the first and third electrodes (or electrodeportions or sections), wherein an electrically insulating gap separatesthe second and third electrodes (or electrode portions or sections). Insome embodiments, a separator is positioned within the gap between thesecond and third electrodes (or electrode portions or sections). In someembodiments, gaps are included between the first and second electrodes(or electrode portions or sections) and between the second and thirdelectrodes (or electrode portions or sections) to increase a ratio ofmapped tissue surface to ablated tissue surface. In some embodiments,the ratio is between 0.2 and 0.8 (e.g., 0.2-0.3, 0.3-0.4, 0.4-0.5,0.5-0.6, 0.6-0.7, 0.7-0.8, ratios between the foregoing, etc.).

According to some embodiments, the system further comprises means forconnectivity to an electrophysiology recorder. In some embodiments, thesystem is configured to connect to an electrophysiology recorder. Insome embodiments, the system comprises an ablation device, and at leastone of (i) a generator for selectively energizing the device, and (ii)an electrophysiology recorder.

According to some embodiments, a method of delivering energy to anablation device comprises energizing a split tip or split sectionelectrode positioned on a catheter (or other medical instrument), thesplit tip or split section electrode comprising a first electrode and asecond electrode (or electrode portions or sections), the firstelectrode and the second electrode being configured to contact tissue ofa subject and deliver energy sufficient to at least partially ablate thetissue, wherein an electrically insulating gap is positioned between thefirst electrode and the second electrode, the electrically insulatinggap comprising a gap width separating the first and second electrodes,wherein a filtering element electrically couples the first electrode tothe second electrode, and wherein electrically separating the first andsecond electrodes facilitates high-resolution mapping along a targetedanatomical area.

According to some embodiments, the method additionally includesreceiving high-resolution mapping data from the first and secondelectrodes (or electrode portions or sections), the high-resolutionmapping data relating to tissue of a subject adjacent the first andsecond electrodes (or electrode portions or sections). In someembodiments, receiving high-resolution mapping data occurs prior to,during or after energizing a split tip electrode positioned on acatheter.

According to some embodiments, a method of mapping tissue of a subjectincludes receiving high-resolution mapping data using a composite tipelectrode (e.g., split-tip or split-section electrode), said compositetip electrode comprising first and second electrodes or electrodeportions located on a catheter and separated by an electricallyinsulating gap, wherein a filtering element electrically couples thefirst electrode to the second electrode in the operating RF range, andwherein electrically insulating the first and second electrodesfacilitates high-resolution mapping along a targeted anatomical area.

According to some embodiments, the method additionally includesenergizing at least one of the first and second electrodes to deliverenergy sufficient to at least partially ablate the tissue of thesubject. In some embodiments, the high-resolution mapping data relatesto tissue of a subject adjacent the first and second electrodes. In someembodiments, receiving high-resolution mapping data occurs prior to,during or after energizing a split tip or a split section electrodepositioned on a catheter.

According to some embodiments, a separator is positioned within the atleast one electrically insulating gap. In some embodiments, the at leastone separator contacts a proximal end of the first electrode and thedistal end of the second electrode. In some embodiments, the first andsecond electrodes are selectively energized using at least one conductorelectrically coupled to an energy delivery module. In some embodiments,the mapping data is provided to an electrophysiology recorder.

According to some embodiments, a frequency of energy provided to thefirst and second electrodes is in the radiofrequency (RF) range. In someembodiments, the filtering element comprises a capacitor.

In some embodiments, the operating RF frequency range is 200 kHz to 10MHz (e.g., 200-300, 300-400, 400-500, 500-600, 400-600, 600-700,700-800, 800-900, 900-1000 kHz, up to 10 MHz or higher frequenciesbetween the foregoing ranges, etc.). In some embodiments, the filteringelement comprises a capacitor. In some embodiments, the capacitorcomprises a capacitance of 50 to 300 nF (e.g., 100 nF, 50-100, 100-150,150-200, 200-250, 250-300 nF, values between the foregoing ranges,etc.). In some embodiments, a series impedance of less than 3 ohms (Ω)(e.g., 0-1, 1-2, 2-3 ohms, values between the foregoing ranges, etc.) isintroduced across the first and second electrodes (or electrode portionsor sections) at 500 kHz.

According to some embodiments, a series impedance introduced across thefirst and second electrodes is lower than: (i) an impedance of aconductor that electrically couples the electrodes to an energy deliverymodule, and (ii) an impedance of a tissue being treated. In someembodiments, the gap width is approximately 0.2 to 1.0 mm (e.g., 0.2,0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0mm, values between the foregoing ranges, less than 0.2 mm, greater than1 mm, etc.). In one embodiment, the gap width is 0.5 mm.

According to some embodiments, a kit for ablation and high-resolutionmapping of cardiac tissue, comprising a device for high-resolutionmapping, the device further being configured to provide ablative energyto targeted tissue, the device comprising an elongate body (e.g.,catheter, other medical instrument, etc.) comprising a proximal end anda distal end, the elongate body comprising an electrode assembly, theelectrode assembly comprising a first and second high-resolutionportions, the first high-resolution electrode portion positioned on theelongate body, the second electrode portion being positioned adjacentthe first electrode portion, the first and second electrode portionsbeing configured to contact tissue of a subject, and at least oneelectrically insulating gap positioned between the first electrodeportion and the second electrode portion, the at least one electricallyinsulating gap comprising a gap width separating the first and secondelectrode portions, wherein the first electrode portion is configured toelectrically couple to the second electrode portion using a filteringelement, wherein the filtering element is configured to present a lowimpedance at a frequency used for delivering ablative energy via thefirst and second electrode portions, and wherein the device isconfigured to be positioned within targeted tissue of the subject toobtain high-resolution mapping data related to said tissue when ablativeenergy is not delivered to the first and second electrode portions. Thekit further comprises an energy delivery module configured to generateenergy for delivery to the electrode assembly, and a processorconfigured to regulate the delivery of energy from the energy deliverymodule to the electrode assembly.

According to some embodiments, a kit for ablation and high-resolutionmapping of cardiac tissue comprises an ablation device, an energydelivery module (e.g., a generator) configured to generate energy fordelivery to the electrode assembly, and a processor configured toregulate the delivery of energy from the energy delivery module to theelectrode assembly. In some embodiments, the energy delivery modulecomprises a RF generator. In some embodiments, the energy deliverymodule is configured to couple to the device.

According to some embodiments, a generator for selectively deliveringenergy to an ablation device comprises an energy delivery moduleconfigured to generate ablative energy for delivery to an ablationdevice, and a processor configured to regulate the delivery of energyfrom the energy delivery module to the ablation device.

According to some embodiments, an ablation device comprises an elongatebody (e.g., catheter, other medical instrument, etc.) comprising adistal end, an electrode positioned at the distal end of the elongatebody, and at least one thermal shunt member placing a heat absorptionelement in thermal communication with the electrode to selectivelyremove heat from at least one of the electrode and tissue being treatedby the electrode when the electrode is activated, wherein the at leastone thermal shunt member extends at least partially through an interiorof the electrode to dissipate and remove heat from the electrode duringuse.

According to some embodiments, the at least one thermal shunt member isin thermal communication with at least one fluid conduit extending atleast partially through an interior of the elongate body, the at leastone fluid conduit being configured to place the electrode in fluidcommunication with a fluid source to selectively remove heat from theelectrode and/or tissue of a subject located adjacent the electrode. Insome embodiments, a fluid conduit or passage extends at least partiallythrough an interior of the elongate body. In some embodiments, the fluidconduit or passage extends at least partially through the at least onethermal shunt member. In several configurations, the at least onethermal shunt member is at least partially in thermal communication witha thermally convective fluid. In some embodiments, a flow rate of thethermally convective fluid is less than 15 ml/min in order to maintain adesired temperature along the electrode during an ablation procedure. Insome embodiments, a flow rate of the thermally convective fluid isapproximately less than 10 ml/min in order to maintain a desiredtemperature along the electrode during an ablation procedure. In someembodiments, a flow rate of the thermally convective fluid isapproximately less than 5 ml/min in order to maintain a desiredtemperature along the electrode during an ablation procedure. In someembodiments, the desired temperature along the electrode during anablation procedure is 60 degrees C. In some embodiments, the thermallyconvective fluid comprises blood and/or another bodily fluid.

According to some embodiments, the at least one fluid conduit is indirect thermal communication with the at least one thermal shunt member.In some embodiments, the at least one fluid conduit is not in directthermal communication with the at least one thermal shunt member. Insome embodiments, the at least one fluid conduit comprises at least oneopening, wherein the at least one opening places irrigation fluidpassing through the at least one fluid conduit in direct physicalcontact with at least a portion of the at least one thermal shuntmember. In some embodiments, the at least one opening is located along aperforated portion of the at least one conduit, wherein the perforatedportion of the at least one conduit is located distally to theelectrode. In some embodiments, the at least one fluid conduit is influid communication only with exit ports located along the distal end ofthe elongate body. In several configurations, the at least one fluidconduit directly contacts the at least one thermal shunt member. In someembodiments, the at least one fluid conduit does not contact the atleast one thermal shunt member.

According to some embodiments, the at least one thermal shunt membercomprises a thermal diffusivity greater than 1.5 cm²/sec. In someembodiments, the at least one thermal shunt member comprises diamond(e.g., an industrial-grade diamond). In other embodiments, the at leastone thermal shunt member comprises a carbon-based material (e.g.,Graphene, silica, etc.). In some embodiments, a temperature of the atleast one thermal shunt member does not exceed 60 to 62 degrees Celsiuswhile maintaining a desired temperature along the electrode during anablation procedure. In some embodiments, the desired temperature alongthe electrode during an ablation procedure is 60 degrees C.

According to some embodiments, the electrode comprises a radiofrequency(RF) electrode. In some embodiments, the electrode comprises a compositeelectrode (e.g., split-tip or split-section electrode). In severalconfigurations, the composite electrode comprises a first electrodeportion and at least a second electrode portion, wherein an electricallyinsulating gap is located between the first electrode portion and the atleast a second electrode portion to facilitate high-resolution mappingalong a targeted anatomical area.

According to some embodiments, at least a portion of the at least onethermal shunt member extends to an exterior of the catheter adjacent theproximal end of the electrode. In some embodiments, at least a portionof the at least one thermal shunt member extends to an exterior of thecatheter adjacent the distal end of the electrode. In some embodiments,at least a portion of the at least one thermal shunt member extendsproximally relative to the proximal end of the electrode. In someembodiments, the at least one thermal shunt member comprises a disk orother cylindrically-shaped member. In some embodiments, the at least onethermal shunt member comprises at least one extension member extendingoutwardly from a base member.

According to some embodiments, the at least one fluid conduit comprisesat least one fluid delivery conduit and at least one fluid returnconduit, wherein the fluid is at least partially circulated through aninterior of the elongate body via the at least one fluid deliveryconduit and the at least one fluid return conduit, wherein the at leastone fluid conduit is part of a closed-loop or non-open cooling system.In some embodiments, the elongate body comprises a cooling chamber alonga distal end of the elongate body, wherein the cooling chamber isconfigured to be in fluid communication with the at least one fluidconduit. In some embodiments, the at least one fluid conduit comprises ametallic material, an alloy and/or the like. In some embodiments, theelongate body does not comprise a fluid conduit. In some embodiments, aninterior of a distal end of the elongate body comprises an interiormember generally along a location of the electrode. In some embodiments,the interior member comprises at least one thermally conductive materialconfigured to dissipate and/or transfer heat generated by the electrode.

According to some embodiments, an ablation device comprises an elongatebody (e.g., catheter, other medical instrument, etc.) including a distalend, an ablation member positioned at the distal end of the elongatebody, and at least one thermal shunt member placing a heat shuntingelement in thermal communication with the electrode to selectivelyremove heat from at least a portion of the electrode and/or tissue beingtreated by the electrode when the electrode is activated, wherein theheat shunting element of the at least one thermal shunt extends at leastpartially through an interior of the ablation member to help remove anddissipate heat generated by the ablation member during use.

According to several embodiments, the at least one thermal shunt memberis in thermal communication with at least one fluid conduit or passageextending at least partially through an interior of the elongate body,the at least one fluid conduit or passage being configured to place theablation member in fluid communication with a fluid source toselectively remove heat from the ablation member and/or tissue of asubject located adjacent the ablation member. In some embodiments, theat least one thermal shunt member comprises at least one fluid conduitor passage extending at least partially through an interior of theelongate body. In some embodiments, the at least one thermal shuntmember does not comprise a fluid conduit or passage extending at leastpartially through an interior of the elongate body. In some embodiments,an interior of the distal end of the elongate body comprises an interiormember generally along a location of the ablation member. In severalconfigurations, the interior member comprises at least one thermallyconductive material configured to dissipate and/or transfer heatgenerated by the ablation member.

According to some embodiments, the ablation member comprises aradiofrequency (RF) electrode. In some embodiments, the ablation membercomprises one of a microwave emitter, an ultrasound transducer and acryoablation member.

According to some embodiments, the at least one thermal shunt membercomprises a thermal diffusivity greater than 1.5 cm²/sec (e.g., greaterthan 1.5 cm²/sec or 5 cm²/sec (e.g., 1.5-2, 2-2.5, 2.5-3, 3-4, 4-5, 5-6,6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-20 cm²/sec,values between the foregoing ranges, greater than 20 cm²/sec). In somearrangements, the at least one thermal shunt member comprises a thermaldiffusivity greater than 5 cm²/sec. In some embodiments, the at leastone thermal shunt member comprises a diamond (e.g., an industrial-gradediamond). In some embodiments, the at least one thermal shunt membercomprises a carbon-based material (e.g., Graphene, silica, etc.). Insome embodiments, the radiofrequency (RF) electrode comprises acomposite electrode (e.g., a split-tip RF electrode or otherhigh-resolution electrode).

According to some embodiments, the at least one fluid conduit or passageis in direct thermal communication with the at least one thermal shuntmember. In some embodiments, the at least one irrigation conduit is notin direct thermal communication with the at least one thermal shuntmember. In some arrangements, the at least one fluid conduit or passagedirectly contacts the at least one thermal shunt member. In someembodiments, the at least one fluid conduit or passage does not contactthe at least one thermal shunt member. In some embodiments, the at leastone fluid conduit or passage comprises at least one opening, wherein theat least one opening places irrigation fluid passing through the atleast one fluid conduit or passage in direct physical contact with atleast a portion of the at least one thermal shunt member. In someembodiments, the at least one opening is located along a perforatedportion of the at least one conduit or passage, wherein the perforatedportion of the at least one conduit or passage is located distally tothe electrode.

According to some embodiments, at least a portion of the at least onethermal shunt member extends to an exterior of the catheter adjacent theproximal end of the ablation member. In some embodiments, at least aportion of the at least one thermal shunt member extends to an exteriorof the catheter adjacent the distal end of the ablation member. In someembodiments, at least a portion of the at least one thermal shunt memberextends proximally relative to the proximal end of the ablation member.In some embodiments, the at least one thermal shunt member comprises adisk or other cylindrically-shaped member. In several configurations,the at least one thermal shunt member comprises at least one extensionmember extending outwardly from a base member. In some embodiments, theat least one extension member comprises at least one of a fin, a pin ora wing. In some embodiments, the at least one fluid conduit or passagecomprises a metallic material.

According to some embodiments, a method of heat removal from an ablationmember during a tissue treatment procedure includes activating anablation system, the system comprising an elongate body (e.g., catheter,other medical instrument, etc.) comprising a distal end, an ablationmember positioned at the distal end of the elongate body, wherein theelongate body of the ablation system comprises at least one thermalshunt member along its distal end, wherein the at least one thermalshunt member extends at least partially through an interior of theablation member, and at least partially removing heat generated by theablation member along the distal end of the elongate body via the atleast one thermal shunt member so as to reduce the likelihood oflocalized hot spots along the distal end of the elongate body.

According to some embodiments, the elongate body further comprises atleast one fluid conduit or passage extending at least partially throughan interior of the elongate body, wherein the method further comprisesdelivering fluid through the at least one fluid conduit or passage,wherein the at least one thermal shunt member places the at least onefluid conduit or passage in thermal communication with a proximalportion of the ablation member to selectively remove heat from theproximal portion of the ablation member when the electrode is activated,wherein the at least one fluid conduit or passage is configured to placethe ablation member in fluid communication with a fluid source toselectively remove heat from the ablation member and/or tissue of asubject located adjacent the ablation member.

According to some embodiments, the elongate body is advanced to a targetanatomical location of the subject through a bodily lumen of thesubject. In some embodiments, the bodily lumen of the subject comprisesa blood vessel, an airway or another lumen of the respiratory tract, alumen of the digestive tract, a urinary lumen or another bodily lumen.In some embodiments, the ablation member comprises a radiofrequency (RF)electrode. In other arrangements, the ablation member comprises one of amicrowave emitter, an ultrasound transducer and a cryoablation member.

According to some embodiments, the at least one thermal shunt membercomprises a thermal diffusivity greater than 1.5 cm²/sec (e.g., greaterthan 1.5 cm²/sec or 5 cm²/sec (e.g., 1.5-2, 2-2.5, 2.5-3, 3-4, 4-5, 5-6,6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-20 cm²/sec,values between the foregoing ranges, greater than 20 cm²/sec). In somearrangements, the at least one thermal shunt member comprises a thermaldiffusivity greater than 5 cm²/sec. In some embodiments, the at leastone thermal shunt member comprises a diamond (e.g., an industrial-gradediamond). In some embodiments, the at least one thermal shunt membercomprises a carbon-based material (e.g., Graphene, silica, etc.). Insome embodiments, the radiofrequency (RF) electrode comprises acomposite electrode (e.g., split-tip RF electrode or otherhigh-resolution electrode). In some embodiments, the method additionallyincludes obtaining at least one high-resolution image of the targetanatomical locations of the subject adjacent the ablation member.

According to some embodiments, the at least one fluid conduit or passageis in direct thermal communication with the at least one thermal shuntmember. In some embodiments, the at least one irrigation conduit is notin direct thermal communication with the at least one thermal shuntmember. According to some embodiments, the at least one fluid conduit orpassage directly contacts the at least one thermal shunt member. In someembodiments, the at least one fluid conduit or passage does not contactthe at least one thermal shunt member. In some embodiments, deliveringfluid through the at least one fluid conduit or passage comprisesdelivering fluid to and through the distal end of the catheter in anopen irrigation system. In several configurations, delivering fluidthrough the at least one fluid conduit or passage includes circulatingfluid through the distal end of the catheter adjacent the ablationmember in a closed fluid cooling system.

According to some embodiments, the elongate body of the ablation systemdoes not comprise any fluid conduits or passages. In one embodiment, theelongate body comprises an interior member. In some embodiments, theinterior member comprises a thermally conductive material that is inthermal communication with the at least one thermal shunt member to helpdissipate and distribute heat generated by the ablation member duringuse. In some embodiments, at least a portion of the at least one thermalshunt member extends to an exterior of the catheter adjacent theproximal end of the ablation member. In some embodiments, at least aportion of the at least one thermal shunt member extends proximally tothe proximal end of the ablation member. In some embodiments, at least aportion of the at least one thermal shunt member extends distally to theproximal end of the ablation member such that at least a portion of theat least one thermal shunt member is located along a length of theablation member. In several configurations, the at least one thermalshunt member comprises a disk or other cylindrically-shaped member. Insome arrangements, the at least one thermal shunt member comprises atleast one extension member extending outwardly from a base member. Insome embodiments, the at least one extension member comprises at leastone of a fin, a pin, a wing and/or the like.

According to some embodiments, a system comprises means for connectivityto an electrophysiology recorder. In some embodiments, the system isconfigured to connect to an electrophysiology recorder. In someembodiments, the system further comprises at least one of (i) agenerator for selectively energizing the device, and (ii) anelectrophysiology recorder. In some embodiments, the system furthercomprises both (i) a generator for selectively energizing the device,and (ii) an electrophysiology recorder.

According to some embodiments, a system for delivering energy totargeted tissue of a subject includes a catheter having ahigh-resolution electrode (e.g., a composite electrode such as asplit-tip or split-section electrode). The composite electrode caninclude two or more electrodes or electrode portions that are separatedby an electrically-insulating gap. A filtering element can electricallycouple the first and second electrodes or electrode portions, or anyadjacent electrode sections (e.g., in a circumferential or radialarrangement) and can be configured to present a low impedance (e.g.,effectively shorting the two electrodes, portions or sections) at afrequency used for delivering ablative energy via the first and secondelectrodes or electrode portions. In some embodiments, electricallyseparating the first and second electrodes, or electrode portions (e.g.,in a circumferential or radial arrangement), facilitates high-resolutionmapping along a targeted anatomical area. The catheter can furtherinclude a plurality of temperatures sensors (e.g., thermocouples) thatare thermally insulated from the electrode and are configured to detecttissue temperature at a depth. The catheter can also include one or morethermal shunt members and/or components for transferring heat away fromthe electrode and/or the tissue being treated. In some embodiments, suchthermal shunt members and/or components include diamond (e.g.,industrial diamond) and/or other materials with favorable thermaldiffusivity characteristics. Further, the system can be configured todetect whether and to what extent contact has been achieved between theelectrode and targeted tissue.

According to some embodiments, an energy delivery device (e.g., ablationdevice) comprises an elongate body (e.g., a catheter) comprising aproximal end and a distal end, a first electrode (e.g., radiofrequencyelectrode) positioned at the distal end of the elongate body, and one ormore second electrodes (e.g., radiofrequency electrodes) positioned at alocation proximal to the first electrode, the first electrode and thesecond electrode being configured to contact tissue of a subject anddeliver radiofrequency energy sufficient to at least partially ablatethe tissue. In alternative embodiments, the electrodes are distributedor otherwise located circumferentially around the catheter (e.g., alongfour quadrant sections distributed around the catheter shaftcircumference separated by gaps). In other embodiments, the catheter mayhave additional support structures and may employ multiple electrodesdistributed on the support structures. The device further comprises atleast one electrically insulating gap positioned between the firstelectrode and the second electrode or the sections of circumferentialelectrodes, the at least one electrically insulating gap comprising agap width separating the first and second electrodes, and a band-passfiltering element electrically coupling the first electrode to thesecond electrode, or any adjacent electrode sections (e.g., in acircumferential or radial arrangement), and configured to present a lowimpedance (e.g., effectively shorting the two electrodes or sections) ata frequency used for delivering ablative energy via the first and secondelectrodes. In some embodiments, electrically separating the first andsecond electrodes, or electrode sections (e.g., in a circumferential orradial arrangement), facilitates high-resolution mapping along atargeted anatomical area. In some embodiments, the ratio of ablatedtissue surface to that of mapped tissue is enhanced (e.g., optimized).

Several embodiments disclosed in the present application areparticularly advantageous because they include one, more or all of thefollowing benefits: a system configured to deliver energy (e.g.,ablative or other type of energy) to anatomical tissue of a subject andconfigured for high-resolution mapping; a system configured to deliverenergy to anatomical tissue of a subject and configured to detect theeffectiveness of the resulting treatment procedure using itshigh-resolution mapping capabilities and functions; a composite tipdesign (e.g., split-tip or split-section design) can be configured to beenergized as a unitary tip or section to more uniformly provide energyto targeted anatomical tissue of a subject and/or the like.

According to some embodiments, the device further comprises a separatorpositioned within the at least one electrically insulating gap. In someembodiments, the at least one separator contacts a proximal end of thefirst electrode and the distal end of the second electrode. In someembodiments, the separator contacts, at least partially, a side of oneelectrode section and an opposing side of the adjacent electrodesection. In one embodiment, the first and second electrodes and theseparator are cylindrical. In one embodiment, the outer diameter of theelectrodes and the separator are equal. In some embodiments, the firstand second electrodes include quadrants or other sections that arecircumferentially distributed on the catheter shaft. In someembodiments, the first and second electrodes comprise other geometriesthat make suitable for distribution on a catheter shaft and also beseparated by a narrow non-conductive gap. In some embodiments, thedevice further comprises at least one conductor (e.g., wire, cable,etc.) configured to electrically couple an energy delivery module (e.g.,a RF or other generator) to at least one of the first and secondelectrodes. In some embodiments, the device further comprises one ormore additional conductors connected to each of the first and secondelectrodes for distributing signals (e.g., cardiac signals) picked up bysaid electrodes to an electrophysiology (EP) recorder.

According to some embodiments, a device additionally includes anelectrophysiology recorder. In some embodiments, a frequency of energyprovided to the first and second electrodes is in an operatingradiofrequency (RF) range (e.g., approximately 300 kHz to 10 MHz).

According to some embodiments, the band-pass filtering element comprisesa capacitor. In some embodiments, the capacitor comprises a capacitanceof 50 to 300 nF (e.g., 100 nF, 50-100, 100-150, 150-200, 200-250,250-300 nF, values between the foregoing ranges, etc.), depending, e.g.,on the operating frequency used to deliver ablative energy. In someembodiments, a series impedance of about 3 ohms (0) or less than about 3ohms (e.g., 0-1, 1-2, 2-3 ohms, values between the foregoing ranges,etc.) is introduced between the first and second electrodes in theoperating RF frequency range (e.g., 300 kHz to 10 MHz). For example, alower capacitance value (e.g. 5-10 nF) may be used at a higher frequencyrange (e.g. 10 MHz). In some embodiments, a 100 nF capacitance value maybe well-suited for applications in the 500 kHz frequency range. In someembodiments, a series impedance introduced across the first and secondelectrodes is lower than: (i) an impedance of a conductor thatelectrically couples the electrodes to an energy delivery module, and(ii) an impedance of a tissue being treated. In some embodiments, thedevice further comprises a band-pass filtering element electricallycoupling the second electrode to the third electrode, or any adjacentelectrode sections (e.g., in a circumferential or radial arrangement),and configured to present a low impedance at a frequency used fordelivering ablative energy via the second and third electrodes.

According to some embodiments, the gap width between the first andsecond electrodes is approximately 0.2 to 1.0 mm (e.g., 0.5 mm). In someembodiments, the elongate body comprises at least one irrigationpassage, said at least one irrigation passage extending to the firstelectrode. In one embodiment, the first electrode comprises at least oneoutlet port in fluid communication with the at least one irrigationpassage.

According to some embodiments, the device further comprises a thirdelectrode, wherein the second electrode is positioned axially betweenthe first and third electrodes, wherein an electrically insulating gapseparates the second and third electrodes. In some embodiments, thedevice further comprises a separator positioned within the gap betweenthe second and third electrodes.

According to some embodiments, a system comprises an ablation deviceaccording to any of the embodiments disclosed herein. In someembodiments, the system additionally comprises means for connectivity toan electrophysiology recorder. In some embodiments, the system isconfigured to connect to an electrophysiology recorder. In someembodiments, the system further comprises at least one of (i) agenerator for selectively energizing the device, and (ii) anelectrophysiology recorder.

According to some embodiments, a method of simultaneously deliveringenergy to an ablation device and mapping tissue of a subject comprisesenergizing a composite electrode (e.g., split-tip electrode,split-section electrode, etc.) being separated by a non-conductive gapfrom the first electrode and a second electrode, the second electrodepositioned at a location proximal to the first electrode, the firstelectrode and the second electrode being configured to contact tissue ofa subject to deliver energy sufficient to at least partially ablate thetissue and to receive high-resolution mapping data, the high-resolutionmapping data relating to tissue of a subject adjacent the first andsecond electrodes. In some embodiments, an electrically insulating gapis positioned between the first electrode and the second electrode, theelectrically insulating gap comprising a gap width separating the firstand second electrodes. In some embodiments, a filtering elementelectrically couples the first electrode to the second electrode only inthe operating RF frequency range. In one embodiment, electricallyseparating the first and second electrodes facilitates high-resolutionmapping along a targeted anatomical area.

According to some embodiments, a separator is positioned within the atleast one electrically insulating gap. In one embodiment, the at leastone separator contacts a proximal end of the first electrode and thedistal end of the second electrode.

According to some embodiments, the mapping data is provided to anelectrophysiology recorder. In some embodiments, a frequency of energyprovided to the first and second electrodes is in the radiofrequencyrange.

According to some embodiments, the filtering element comprises acapacitor. In one embodiment, the capacitor comprises a capacitance of50 to 300 nF (e.g., 100 nF), depending on, e.g., the operating frequencyused for ablative energy. In some embodiments, a series impedance ofabout 3 ohms (Ω) is introduced across the first and second electrodes at500 kHz. In some embodiments, a series impedance introduced across thefirst and second electrodes is lower than: (i) an impedance of aconductor that electrically couples the electrodes to an energy deliverymodule, and (ii) an impedance of a tissue being treated.

According to some embodiments, the gap width is approximately 0.2 to 1.0mm. In one embodiment, the gap width is 0.5 mm.

According to some embodiments, an ablation device comprises an elongatebody (e.g., catheter, other medical instrument, etc.) comprising adistal end, an electrode positioned at the distal end of the elongatebody and at least one thermal shunt member placing a heat absorptionelement in thermal communication with the electrode to selectivelyremove heat from at least one of the electrode and tissue being treatedby the electrode when the electrode is activated, wherein the at leastone thermal shunt member extends at least partially through an interiorof the electrode to dissipate and remove heat from the electrode duringuse. In some embodiments, the at least one thermal shunt member is inthermal communication with at least one fluid conduit extending at leastpartially through an interior of the elongate body, the at least onefluid conduit being configured to place the electrode in fluidcommunication with a fluid source to selectively remove heat from theelectrode and/or tissue of a subject located adjacent the electrode. Insome embodiments, a fluid conduit or passage extends at least partiallythrough an interior of the elongate body. In one embodiment, the fluidconduit or passage extends at least partially through the at least onethermal shunt member. In some embodiments, the at least one thermalshunt member is at least partially in thermal communication with athermally convective fluid. In some embodiments, the thermallyconvective fluid comprises blood and/or another bodily fluid.

According to some embodiments, a flow rate of the thermally convectivefluid is less than 15 ml/min in order to maintain a desired temperaturealong the electrode during an ablation procedure. In some embodiments, aflow rate of the thermally convective fluid is approximately less than10 ml/min in order to maintain a desired temperature along the electrodeduring an ablation procedure. In some embodiments, a flow rate of thethermally convective fluid is approximately less than 5 ml/min in orderto maintain a desired temperature along the electrode during an ablationprocedure. According to some embodiments, the desired temperature alongthe electrode during an ablation procedure is 60 degrees C.

According to some embodiments, the at least one thermal shunt membercomprises a thermal diffusivity greater than 1.5 cm²/sec or 5 cm²/sec(e.g., 1.5-2, 2-2.5, 2.5-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11,11-12, 12-13, 13-14, 14-15, 15-20 cm²/sec, values between the foregoingranges, greater than 20 cm²/sec). In some embodiments, the at least onethermal shunt member comprises diamond (e.g., an industrial-gradediamond). In some embodiments, the at least one thermal shunt membercomprises a carbon-based material. In some embodiments, the at least onethermal shunt member comprises at least one of Graphene and silica.

According to some embodiments, a temperature of the at least one thermalshunt member does not exceed 60 to 62 degrees Celsius while maintaininga desired temperature along the electrode during an ablation procedure.In some embodiments, the desired temperature along the electrode duringan ablation procedure is 60 degrees C.

According to some embodiments, the electrode comprises a radiofrequency(RF) electrode. In some embodiments, the electrode comprises a compositeelectrode (e.g., split-tip electrode). In some embodiments, thecomposite electrode comprises a first electrode portion and at least asecond electrode portion, wherein an electrically insulating gap islocated between the first electrode portion and the at least a secondelectrode portion to facilitate high-resolution mapping along a targetedanatomical area.

According to some embodiments, the at least one fluid conduit is indirect thermal communication with the at least one thermal shunt member.In some embodiments, the at least one fluid conduit is not in directthermal communication with the at least one thermal shunt member. Insome embodiments, the at least one fluid conduit comprises at least oneopening, wherein the at least one opening places irrigation fluidpassing through the at least one fluid conduit in direct physicalcontact with at least a portion of the at least one thermal shuntmember. In some embodiments, the at least one opening is located along aperforated portion of the at least one conduit, wherein the perforatedportion of the at least one conduit is located distally to theelectrode. In one embodiment, the at least one fluid conduit is in fluidcommunication only with exit ports located along the distal end of theelongate body. In some embodiments, the at least one fluid conduitdirectly contacts the at least one thermal shunt member. In someembodiments, the at least one fluid conduit does not contact the atleast one thermal shunt member. In some embodiments, at least a portionof the at least one thermal shunt member extends to an exterior of thecatheter adjacent the proximal end of the electrode. In one embodiment,at least a portion of the at least one thermal shunt member extends toan exterior of the catheter adjacent the distal end of the electrode. Incertain embodiments, at least a portion of the at least one thermalshunt member extends proximally relative to the proximal end of theelectrode. In some embodiments, the at least one thermal shunt membercomprises a disk or other cylindrically-shaped member.

According to some embodiments, an ablation device comprises an elongatebody (e.g., catheter, other medical instrument, etc.) comprising adistal end, an ablation member positioned at the distal end of theelongate body and at least one thermal shunt member placing a heatshunting element in thermal communication with the electrode toselectively remove heat from at least a portion of the electrode and/ortissue being treated by the electrode when the electrode is activated,wherein the heat shunting element of the at least one thermal shuntextends at least partially through an interior of the ablation member tohelp remove and dissipate heat generated by the ablation member duringuse. In some embodiments, the at least one thermal shunt member is inthermal communication with at least one fluid conduit or passageextending at least partially through an interior of the elongate body,the at least one fluid conduit or passage being configured to place theablation member in fluid communication with a fluid source toselectively remove heat from the ablation member and/or tissue of asubject located adjacent the ablation member.

According to some embodiments, the at least one thermal shunt membercomprises at least one fluid conduit or passage extending at leastpartially through an interior of the elongate body. In some embodiments,the at least one thermal shunt member does not comprise a fluid conduitor passage extending at least partially through an interior of theelongate body. In some embodiments, an interior of the distal end of theelongate body comprises an interior member generally along a location ofthe ablation member. In one embodiment, the interior member comprises atleast one thermally conductive material configured to dissipate and/ortransfer heat generated by the ablation member.

According to some embodiments, the ablation member comprises aradiofrequency (RF) electrode. In some embodiments, the ablation membercomprises one of a microwave emitter, an ultrasound transducer and acryoablation member.

According to some embodiments, the at least one thermal shunt membercomprises at least one extension member extending outwardly from a basemember. In some embodiments, the at least one fluid conduit comprises atleast one fluid delivery conduit and at least one fluid return conduit,wherein the fluid is at least partially circulated through an interiorof the elongate body via the at least one fluid delivery conduit and theat least one fluid return conduit, wherein the at least one fluidconduit is part of a closed-loop or non-open cooling system. In someembodiments, the elongate body comprises a cooling chamber along adistal end of the elongate body, wherein the cooling chamber isconfigured to be in fluid communication with the at least one fluidconduit. In some embodiments, the at least one fluid conduit comprisesat least one of a metallic material and an alloy. In some embodiments,the elongate body does not comprise a fluid conduit. In one embodiment,an interior of a distal end of the elongate body comprises an interiormember generally along a location of the electrode. In some embodiments,the interior member comprises at least one thermally conductive materialconfigured to dissipate and/or transfer heat generated by the electrode.

According to some embodiments, a method of heat removal from an ablationmember during a tissue treatment procedure comprises activating anablation system, the system comprising an elongate body comprising adistal end, an ablation member positioned at the distal end of theelongate body, wherein the elongate body of the ablation systemcomprises at least one thermal shunt member along its distal end,wherein the at least one thermal shunt member extends at least partiallythrough an interior of the ablation member, and at least partiallyremoving heat generated by the ablation member along the distal end ofthe elongate body via the at least one thermal shunt member so as toreduce the likelihood of localized hot spots along the distal end of theelongate body.

According to some embodiments, the elongate body (e.g., catheter,medical instrument, etc.) further comprises at least one fluid conduitor passage extending at least partially through an interior of theelongate body, the method further comprising delivering fluid throughthe at least one fluid conduit or passage, wherein the at least onethermal shunt member places the at least one fluid conduit or passage inthermal communication with a proximal portion of the ablation member toselectively remove heat from the proximal portion of the ablation memberwhen the electrode is activated, wherein the at least one fluid conduitor passage is configured to place the ablation member in fluidcommunication with a fluid source to selectively remove heat from theablation member and/or tissue of a subject located adjacent the ablationmember.

According to some embodiments, the elongate body is advanced to a targetanatomical location of the subject through a bodily lumen of thesubject. In some embodiments, the bodily lumen of the subject comprisesa blood vessel, an airway or another lumen of the respiratory tract, alumen of the digestive tract, a urinary lumen or another bodily lumen.In some embodiments, the ablation member comprises a radiofrequency (RF)electrode. In some embodiments, the ablation member comprises one of amicrowave emitter, an ultrasound transducer and a cryoablation member.In some embodiments, the at least one thermal shunt member comprises athermal diffusivity greater than 1.5 cm²/sec or 5 cm²/sec (e.g., 1.5-2,2-2.5, 2.5-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13,13-14, 14-15, 15-20 cm²/sec, values between the foregoing ranges,greater than 20 cm²/sec). In some embodiments, the at least one thermalshunt member comprises diamond (e.g., an industrial-grade diamond). Insome embodiments, the at least one thermal shunt member comprises acarbon-based material. In some embodiments, the at least one thermalshunt member comprises at least one of Graphene and silica.

According to some embodiments, the radiofrequency (RF) electrodecomprises a composite RF electrode (e.g., split-tip RF electrode). Insome embodiments, the method further comprises obtaining at least onehigh-resolution image of the target anatomical locations of the subjectadjacent the ablation member. In some embodiments, the at least onefluid conduit or passage is in direct thermal communication with the atleast one thermal shunt member. In some embodiments, the at least oneirrigation conduit is not in direct thermal communication with the atleast one thermal shunt member. In some embodiments, the at least onefluid conduit or passage directly contacts the at least one thermalshunt member. In one embodiment, the at least one fluid conduit orpassage does not contact the at least one thermal shunt member. Incertain embodiments, delivering fluid through the at least one fluidconduit or passage comprises delivering fluid to and through the distalend of the catheter in an open irrigation system. In some embodiments,delivering fluid through the at least one fluid conduit or passagecomprises circulating fluid through the distal end of the catheteradjacent the ablation member in a closed fluid cooling system.

According to some embodiments, the elongate body (e.g., catheter,medical instrument, etc.) of the ablation system does not comprise anyfluid conduits or passages. In some embodiments, the distal end of theelongate body comprises an interior member. In some embodiments, theinterior member comprises a thermally conductive material that is inthermal communication with the at least one thermal shunt member to helpdissipate and distribute heat generated by the ablation member duringuse. In some embodiments, at least a portion of the at least one thermalshunt member extends to an exterior of the catheter adjacent theproximal end of the ablation member. In one embodiment, at least aportion of the at least one thermal shunt member extends proximally tothe proximal end of the ablation member. In some embodiments, at least aportion of the at least one thermal shunt member extends distally to theproximal end of the ablation member such that at least a portion of theat least one thermal shunt member is located along a length of theablation member. In some embodiments, the at least one thermal shuntmember comprises a disk or other cylindrically-shaped member. In oneembodiment, the at least one thermal shunt member comprises at least oneextension member extending outwardly from a base member. In someembodiments, the at least one extension member comprises at least one ofa fin, a pin or a wing.

According to some embodiments, a system comprising a device inaccordance with the present application further comprises means forconnectivity to an electrophysiology recorder. In some embodiments, thesystem is configured to connect to an electrophysiology recorder. Insome embodiments, the system further comprises at least one of (i) agenerator for selectively energizing the device, and (ii) anelectrophysiology recorder.

According to some embodiments, an ablation device comprises an elongatebody (e.g., a catheter) having a distal end, an electrode (e.g., a RFelectrode, composite electrode, etc.) positioned at the distal end ofthe elongate body, at least one irrigation conduit extending at leastpartially through an interior of the elongate body, the at least oneirrigation conduit configured to place the electrode in fluidcommunication with a fluid source to selectively remove heat from theelectrode and/or tissue of a subject located adjacent the electrode andat least one heat transfer member placing the at least one irrigationconduit in thermal communication with a proximal portion of theelectrode to selectively remove heat from the proximal portion of theelectrode when the electrode is activated.

According to some embodiments, an ablation device comprises an elongatebody (e.g., a catheter, other medical instrument, etc.) comprising adistal end, an ablation member positioned at the distal end of theelongate body, at least one irrigation conduit extending at leastpartially through an interior of the elongate body, the at least oneirrigation conduit configured to place the ablation member in fluidcommunication with a fluid source and at least one thermal transfermember placing the at least one irrigation conduit in thermalcommunication with a proximal portion of the ablation member toselectively remove heat from the proximal portion of the ablation memberwhen the electrode is activated. In some embodiments, the ablationmember comprises a radiofrequency (RF) electrode, a microwave emitter,an ultrasound transducer, a cryoablation member and/or any other member.

According to some embodiments, the at least one thermal transfer membercomprises a thermal conductance greater than 300 W/m/° C. (e.g.,300-350, 350-400, 400-450, 450-500 W/m/° C., ranges between theforegoing, etc.). In other embodiments, the at least one thermaltransfer member comprises a thermal conductance greater than 500 W/m/°C. (e.g., 500-550, 550-600, 600-650, 650-700, 700-800, 800-900, 900-1000W/m/° C., ranges between the foregoing, greater than 1000 W/m/° C.,etc.).

According to some embodiments, the at least one thermal transfer membercomprises a diamond (e.g., industrial-grade diamond). In someembodiments, the at least one thermal transfer member comprises at leastone of a metal and an alloy (e.g., copper, beryllium, brass, etc.).

According to some embodiments, the electrode comprises a radiofrequency(RF) electrode. In one embodiment, the electrode comprises a compositeelectrode (e.g., a split-tip electrode). In some embodiments, thecomposite electrode comprises a first electrode portion and at least asecond electrode portion, wherein an electrically insulating gap islocated between the first electrode portion and the at least a secondelectrode portion to facilitate high-resolution mapping along a targetedanatomical area.

According to some embodiments, the device further comprises aradiometer. In some embodiments, the radiometer is located in thecatheter (e.g., at or near the electrode or other ablation member). Inother embodiments, however, the radiometer is located in the handle ofthe device and/or at another location of the device and/or accompanyingsystem. In embodiments of the device that comprise a radiometer, thecatheter comprises one or more antennas (e.g., at or near the electrode)configured to detect microwave signals emitted by tissue. In someembodiments, the device does not comprise a radiometer or does notincorporate radiometry technology (e.g., for measuring temperature oftissue). As discussed herein, other types of temperature-measurementdevices (e.g., thermocouples, thermistors, other temperature sensors,etc.) can be incorporate into a device or system.

According to some embodiments, an ablation device consists essentiallyof a catheter, an ablation member (e.g., a RF electrode, a compositeelectrode, etc.), an irrigation conduit extending through an interior ofthe catheter to or near the ablation member, at least one electricalconductor (e.g., wire, cable, etc.) to selectively activate the ablationmember and at least one heat transfer member that places at least aportion of the ablation member (e.g., a proximal portion of the ablationmember) in thermal communication with the irrigation conduit.

According to some embodiments, an ablation device consists essentiallyof a catheter, an ablation member (e.g., a RF electrode, a compositeelectrode, etc.), an irrigation conduit extending through an interior ofthe catheter to or near the ablation member, at least one electricalconductor (e.g., wire, cable, etc.) to selectively activate the ablationmember, an antenna configured to receive microwave signals emitted bytissue of a subject, a radiometer and at least one heat transfer memberthat places at least a portion of the ablation member (e.g., a proximalportion of the ablation member) in thermal communication with theirrigation conduit.

According to some embodiments, the at least one irrigation conduit is indirect thermal communication with the at least one thermal transfermember. In some embodiments, the at least one irrigation conduit is notin direct thermal communication with the at least one thermal transfermember. In some embodiments, the irrigation conduit is fluidcommunication only with exit ports located along the distal end of theelongate body. In some embodiments, the catheter only comprisesirrigation exit openings along a distal end of the catheter (e.g., alonga distal end or the electrode). In some embodiments, the system does notcomprise any irrigation openings along the heat transfer members.

According to some embodiments, the at least one irrigation conduitdirectly contacts the at least one thermal transfer member. In someembodiments, the at least one irrigation conduit does not contact the atleast one thermal transfer member. In one embodiment, at least a portionof the heat transfer member extends to an exterior of the catheteradjacent the proximal end of the electrode. In some embodiments, atleast a portion of the heat transfer member extends proximally to theproximal end of the electrode. In certain embodiments, at least aportion of the heat transfer member extends distally to the proximal endof the electrode such that at least a portion of the heat transfermember is located along a length of the electrode. According to someembodiments, the at least one irrigation conduit comprises a metallicmaterial and/or other thermally conductive materials.

According to some embodiments, the heat transfer member comprises a diskor other cylindrically-shaped member. In some embodiments, the heattransfer member comprises at least one extension member extendingoutwardly from a base member.

According to some embodiments, the device further comprises a radiometerto enable the device and/or accompanying system to detect a temperatureto tissue of the subject at a depth. In some embodiments, the radiometeris included, at least in part, in the catheter. In other embodiments,the radiometer is located, at least in part, in the handle of the systemand/or in a portion of the device and/or accompanying system external tothe catheter.

According to some embodiments, a method of heat removal from an ablationmember during an ablation procedure comprises activating an ablationsystem, the system comprising an elongate body comprising a distal end,an ablation member positioned at the distal end of the elongate body, atleast one irrigation conduit extending at least partially through aninterior of the elongate body, and at least one thermal transfer member,wherein the at least one irrigation conduit configured to place theablation member in fluid communication with a fluid source toselectively remove heat from the ablation member and/or tissue of asubject located adjacent the ablation member, and delivering fluidthrough the at least one irrigation conduit, wherein the at least onethermal transfer member places the at least one irrigation conduit inthermal communication with a proximal portion of the ablation member toselectively remove heat from the proximal portion of the ablation memberwhen the electrode is activated.

According to some embodiments, the elongate body is advanced to a targetanatomical location of the subject through a bodily lumen of thesubject. In some embodiments, the bodily lumen of the subject comprisesa blood vessel, an airway or another lumen of the respiratory tract, alumen of the digestive tract, a urinary lumen or another bodily lumen.

According to some embodiments, the ablation member comprises aradiofrequency (RF) electrode, a microwave emitter, an ultrasoundtransducer, a cryoablation member and/or the like. In some embodiments,the at least one thermal transfer member comprises a thermal conductancegreater than 300 W/m/° C. In one embodiment, the at least one thermaltransfer member comprises a thermal conductance greater than 500 W/m/°C.

According to some embodiments, the at least one thermal transfer membercomprises a diamond (e.g., industrial-grade diamond). In someembodiments, the at least one thermal transfer member comprises at leastone of a metal and an alloy (e.g., copper, beryllium, brass, etc.).

According to some embodiments, a system comprises an ablation deviceaccording to any of the embodiments disclosed herein. In someembodiments, the system additionally comprises means for connectivity toan electrophysiology recorder. In some embodiments, the system isconfigured to connect to an electrophysiology recorder. In someembodiments, the system further comprises at least one of (i) agenerator for selectively energizing the device, and (ii) anelectrophysiology recorder.

According to one embodiment, a medical instrument (e.g., ablationcatheter) includes an elongate body having a proximal end and a distalend. The medical instrument also includes an energy delivery memberpositioned at the distal end of the elongate body that is configured todeliver energy to the targeted tissue. The medical instrument furtherincludes a first plurality of temperature-measurement devices positionedwithin the energy delivery member and being thermally insulated from theenergy delivery member and a second plurality of temperature-measurementdevices positioned along the elongate body and spaced apart axially fromthe first plurality of temperature-measurement devices, the secondplurality of temperature-measurement devices also being thermallyinsulated from the energy delivery member. The energy delivery membermay optionally be configured to contact the tissue. The first pluralityof temperature-measurement devices may optionally be positioned along afirst plane that is substantially perpendicular to a longitudinal axisof the elongate body. The second plurality of temperature-measurementdevices may optionally be positioned along a second plane that issubstantially perpendicular to a longitudinal axis of the elongate bodyand spaced apart axially along the longitudinal axis proximal to thefirst plane. The energy delivery member may optionally comprise one ormore electrode portions, one or more ultrasound transducers, one or morelaser elements, or one or more microwave emitters.

According to one embodiment, a medical instrument (e.g., an ablationcatheter or other device) comprises an elongate body having a proximalend and a distal end. The medical instrument comprises at least oneenergy delivery member (e.g., a tip electrode or multiple electrodeportions) positioned at the distal end of the elongate body. In thisembodiment, the at least one energy delivery member is configured todeliver energy (e.g., radiofrequency energy, acoustic energy, microwavepower, laser energy) to the targeted tissue with or without contactingthe tissue. In one embodiment, the energy is sufficient to generate alesion at a depth from a surface of the targeted tissue. The embodimentof the medical instrument comprises a first plurality oftemperature-measurement devices carried by, or positioned withinseparate apertures, recesses or other openings formed in a distal end(e.g., a distal-most surface) of the at least one energy deliverymember. The first plurality of temperature-measurement devices arethermally insulated from the energy delivery member. The embodiment ofthe medical instrument comprises a second plurality oftemperature-measurement devices positioned adjacent to (e.g., within 1mm of) a proximal end of the at least one energy delivery member (e.g.,carried by or within the energy delivery member or carried by or withinthe elongate body proximal of the proximal end of the energy deliverymember), the second plurality of temperature-measurement devices beingthermally insulated from the at least one energy delivery member. Thesecond plurality of temperature-measurement devices may be positionedjust proximal or just distal of the proximal end of the at least oneenergy delivery member. If the medical instrument comprises two or moreenergy delivery members, then the second plurality oftemperature-measurement devices may be positioned adjacent the proximaledge of the proximal-most energy delivery member and the first pluralityof temperature-measurement devices may be positioned within thedistal-most energy delivery member. In some embodiments, the secondplurality of temperature-measurement devices are positioned along athermal shunt member (e.g., thermal transfer member) proximal of the atleast one energy delivery member. In some embodiments, the secondplurality of temperature-measurement devices is positioned along a planethat is perpendicular or substantially perpendicular to a longitudinalaxis of the distal end of the elongate body and spaced proximal to thefirst plurality of temperature-measurement devices.

In some embodiments, each of the temperature-measurement devicescomprises a thermocouple or a thermistor (e.g., Type K or Type Tthermocouples). In some embodiments, the first plurality oftemperature-measurement devices comprises at least threetemperature-measurement devices and the second plurality oftemperature-measurement devices comprises at least threetemperature-measurement devices. In one embodiment, the first pluralityof temperature-measurement devices consists of only threetemperature-measurement devices and the second plurality oftemperature-measurement devices consists of only threetemperature-measurement devices. Each of the first plurality oftemperature-measurement devices and each of the second plurality oftemperature-measurement devices may be spaced apart (equidistantly ornon-equally spaced) from each of the other temperature-measurementdevices of its respective group (e.g., circumferentially or radiallyaround an outer surface of the elongate body or otherwise arranged). Forexample, where three temperature-measurement devices are included ineach plurality, group or set, the temperature-measurement devices may bespaced apart by about 120 degrees. In some embodiments, the firstplurality of temperature-measurement devices and the second plurality oftemperature-measurement devices protrude or otherwise extend beyond anouter surface of the elongate body to facilitate increased depth ofinsertion (e.g., burying) within the targeted tissue. In one embodimentthe elongate body is cylindrical or substantially cylindrical. Thedistal ends of the temperature-measurement devices may comprise agenerally rounded casing or shell to reduce the likelihood ofpenetration or scraping of the targeted tissue.

In accordance with one embodiment, a medical instrument (e.g., ablationdevice) comprises an elongate body having a proximal end and a distalend and a combination or high-resolution electrode assembly (e.g., acomposite electrode assembly, such as a split-tip electrode assembly)positioned at the distal end of the elongate body. The compositeelectrode assembly or other high-resolution electrode assembly comprisesa first electrode member positioned at a distal terminus of the distalend of the elongate body, a second electrode member positioned proximalto the first electrode member and spaced apart from the first electrodemember, and an electrically-insulating gap between the first electrodemember and the second electrode member. The first electrode member andthe second electrode member may be configured to contact tissue of asubject and to deliver radiofrequency energy to the tissue. In someembodiments, the energy may be sufficient to ablate the tissue. Theelectrically-insulating gap may comprise a gap width separating thefirst electrode member and the second electrode member. The embodimentof the medical instrument comprises a first plurality of temperaturesensors positioned within separate openings, apertures, slits, slots,grooves or bores formed in the first electrode member and spaced apart(e.g., circumferentially, radially or otherwise) and a second pluralityof temperature sensors positioned at a region proximal to the secondelectrode member (e.g., adjacent to (just proximal or just distal,within less than 1 mm from) a proximal edge of the second electrodemember). Positioning within 1 mm of the proximal edge may advantageouslyprovide more useful or important temperature measurements becausetypically the hottest spots form at the proximal edge of an electrode.The second plurality of temperature sensors are thermally insulated fromthe second electrode member. In some embodiments, the second pluralityof temperature sensors is spaced apart circumferentially or radiallyaround an outer circumferential surface of the elongate body. The firstplurality of temperature sensors may be thermally insulated from thefirst electrode member and may extend beyond an outer surface (e.g.,distal-most surface) of the first electrode member. In one embodiment,at least a portion of each of the second plurality of temperaturesensors extends beyond the outer circumferential surface of the elongatebody.

In some embodiments, the medical instrument comprises a heat exchangechamber (e.g., irrigation conduit) extending at least partially throughan interior of the elongate body. The medical instrument may be coupledto a fluid source configured to supply cooling fluid to the heatexchange chamber and a pump configured to control delivery of thecooling fluid to the heat exchange chamber from the fluid source throughone or more internal lumens within the heat exchange chamber. In oneembodiment, the first electrode member comprises a plurality ofirrigation exit ports in fluid communication with the heat exchangechamber such that the cooling fluid supplied by the fluid source exitsfrom the irrigation exit ports, thereby providing cooling to thecomposite electrode assembly or other high resolution electrodeassembly, blood and/or tissue being heated.

For open irrigation arrangements, the medical instrument (e.g., ablationdevice) may comprise a fluid delivery lumen having a diameter or othercross-sectional dimension smaller than the lumen of the heat exchangechamber (e.g., irrigation conduit) to facilitate increased velocity toexpel the saline or other fluid out of the irrigation exit ports at aregular flow rate. For closed irrigation arrangements, the medicalinstrument may comprise an inlet lumen (e.g., fluid delivery lumen)extending between the heat exchange chamber and the fluid source and anoutlet lumen (e.g., return lumen) extending between the heat exchangechamber (e.g., irrigation conduit) and a return reservoir external tothe medical instrument. In one embodiment, a distal end (e.g., outlet)of the inlet lumen is spaced distally from the distal end (e.g., inlet)of the outlet lumen so as to induce turbulence or other circulationwithin the heat exchange chamber. In various embodiments, an irrigationflow rate is 10 mL/min or less (e.g., 9 mL/min or less, 8 mL/min orless, 7 mL/min or less, 6 mL/min or less, 5 m/min or less). In someembodiments, the medical instruments are not irrigated.

According to one embodiment, a medical instrument (e.g., ablationdevice) comprises an elongate body (e.g., a catheter, wire, probe, etc.)comprising a proximal end and a distal end and a longitudinal axisextending from the proximal end to the distal end. The medicalinstrument comprises a combination or high-resolution electrode assembly(e.g., composite electrode assembly, such as a split-tip electrodeassembly). In the embodiment, the composite electrode assembly comprisesa first electrode member positioned at a distal terminus of the distalend of the elongate body and a second electrode member positionedproximal to the first electrode member and spaced apart from the firstelectrode member. The first electrode member and the second electrodemember are configured to contact tissue of a subject and to deliverradiofrequency energy to the tissue. The energy delivered may besufficient to at least partially ablate or otherwise heat the tissue.The composite electrode assembly also comprises anelectrically-insulating gap comprising a gap width separating the firstelectrode member and the second electrode member. The embodiment of theablation device further comprises at least one thermal transfer memberin thermal communication with the first and second electrode members toselectively remove or dissipate heat from the first and second electrodemembers, a first plurality of temperature-measurement devices positionedwithin the first electrode member and spaced apart (e.g.,circumferentially, radially) and a second plurality oftemperature-measurement devices positioned within a portion of the atleast one thermal heat shunt member (e.g., heat transfer member)proximal to the second electrode member. The first plurality oftemperature-measurement devices is thermally insulated from the firstelectrode member and may extend beyond an outer surface of the firstelectrode member in a direction that is at least substantially parallelto the longitudinal axis of the elongate body. The second plurality ofthermocouples is thermally insulated from the second electrode memberand may extend beyond an outer surface of the at least one thermal heatshunt member in a direction that is at least substantially perpendicularto the longitudinal axis of the elongate body.

In some embodiments, the medical instrument comprises a heat exchangechamber (e.g., irrigation conduit) extending at least partially throughan interior of the elongate body. The medical instrument may be fluidlycoupled to a fluid source configured to supply cooling fluid to the heatexchange chamber and a pump configured to control delivery of thecooling fluid. In one embodiment, the first electrode member comprises aplurality of irrigation exit ports in fluid communication with the heatexchange chamber such that the cooling fluid supplied by the fluidsource is expelled from the irrigation exit ports, thereby providingcooling to the composite electrode assembly (e.g., split-tip electrodeassembly). In some embodiments, at least an inner surface or layer ofthe heat exchange chamber comprises a biocompatible material, such asstainless steel.

In some embodiments, the at least one thermal shunt member (e.g., heatshunt network or heat transfer member(s)) comprises a thermalconductance greater than 300 W/m/° C. (e.g., 300-350, 350-400, 400-450,450-500 W/m/° C., ranges between the foregoing, etc.). In otherembodiments, the at least one thermal transfer member comprises athermal conductance greater than 500 W/m/° C. (e.g., 500-550, 550-600,600-650, 650-700, 700-800, 800-900, 900-1000 W/m/° C., ranges betweenthe foregoing, greater than 1000 W/m/° C., etc.). According to someembodiments, the at least one thermal transfer member comprises adiamond (e.g., industrial-grade diamond).

The electrode member(s) may comprise platinum in any of the embodiments.The temperature-measurement devices may comprise one of more of thefollowing types of thermocouples: nickel alloy, platinum/rhodium alloy,tungsten/rhenium alloy, gold/iron alloy, noble metal alloy,platinum/molybdenum alloy, iridium/rhodium alloy, pure noble metal, TypeK, Type T, Type E, Type J, Type M, Type N, Type B, Type R, Type S, TypeC, Type D, Type G, and/or Type P.

According to some embodiments, the medical instrument comprises at leastone separator positioned within the at least one electrically-insulatinggap. In one embodiment, the at least one separator comprises a portionof the at least one thermal transfer member. For example, the at leastone separator may comprise industrial grade diamond.

According to some embodiments, the medical instrument comprises at leastone conductor configured to conduct current from an energy source to thecomposite electrode assembly (e.g., split-tip electrode assembly) orother ablation members. In some embodiments, the first plurality ofthermocouples or other temperature-measurement devices and the secondplurality of thermocouples or other temperature-measurement devicesextend up to 1 mm beyond the outer surface of the first electrode memberand the at least one thermal transfer member, respectively.

According to some embodiments, an outer diameter of a portion of the atleast one thermal heat transfer member comprising the second pluralityof temperature-measurement devices is greater than the outer diameter ofthe elongate body so as to facilitate greater insertion depth within thetissue, thereby increasing isolation of the thermocouples or othertemperature-measurement devices from the thermal effects of theelectrode member(s).

In accordance with several embodiments, a treatment system comprises amedical instrument (e.g., an ablation catheter), a processor, and anenergy source. The medical instrument comprises an elongate body havinga proximal end and a distal end, an energy delivery member (e.g.,electrode) positioned at the distal end of the elongate body, a firstplurality of temperature-measurement devices carried by or positionedalong or within the energy delivery member, and a second plurality oftemperature-measurement devices positioned proximal of the electrodealong the elongate body. The energy delivery member may be configured tocontact tissue of a subject and to deliver energy generated by theenergy source to the tissue. In some embodiments, the energy issufficient to at least partially ablate the tissue. In some embodiments,the first plurality of temperature-measurement devices are thermallyinsulated from the energy delivery member and the second plurality oftemperature-measurement devices are thermally insulated from the energydelivery member. In one embodiment, the second plurality oftemperature-measurement devices is spaced apart around an outer surfaceof the elongate body. The energy source of the embodiment of the systemmay be configured to provide the energy to the energy delivery memberthrough one or more conductors (e.g., wires, cables, etc.) extendingfrom the energy source to the energy delivery member.

The processor of the embodiment of the system may be programmed orotherwise configured (e.g., by execution of instructions stored on anon-transitory computer-readable storage medium) to receive signals fromeach of the temperature-measurement devices indicative of temperatureand determine an orientation of the distal end of the elongate body ofthe ablation catheter with respect to the tissue based on the receivedsignals. In some embodiments, the processor may be configured to adjustone or more treatment parameters based on the determined orientation.The one or more treatment parameters may include, among other things,duration of treatment, power of energy, target or setpoint temperature,and maximum temperature.

In some embodiments, the processor is configured to cause anidentification of the determined orientation to be output to a display.The output may comprise textual information (such as a word, phrase,letter or number). In some embodiments, the display comprises agraphical user interface and the output comprises one or more graphicalimages indicative of the determined orientation.

In some embodiments, the determination of the orientation of the distalend of the elongate body of the medical instrument with respect to thetissue is based on a comparison of tissue measurements determined fromreceived signals with respect to each other. The orientation may beselected from one of three orientation options: perpendicular, paralleland angled or oblique. In one embodiment, the processor is configured togenerate an output to terminate delivery of energy if the determinedorientation changes during energy delivery (e.g., an alarm to cause auser to manually terminate energy delivery or a signal to automaticallycause termination of energy delivery. In some embodiments, the processormay be configured to adjust one or more treatment parameters based onthe determined orientation. The one or more treatment parameters mayinclude, among other things, duration of treatment, power of energy,target or setpoint temperature, and maximum temperature.

According to some embodiments, a treatment system comprises a medicalinstrument (e.g., an ablation catheter) and a processor. The medicalinstrument may comprise an elongate body having a proximal end and adistal end, an energy delivery member positioned at the distal end ofthe elongate body, the energy delivery member being configured tocontact tissue of a subject and to deliver energy (e.g., ablativeenergy) to the tissue, a first plurality of temperature-measurementdevices positioned within the energy delivery member, and a secondplurality of temperature-measurement devices positioned proximal to theenergy delivery member along the elongate body. The first plurality oftemperature-measurement devices may be thermally insulated from theenergy delivery member and may be spaced apart from each other and thesecond plurality of temperature-measurement devices may be thermallyinsulated from the energy delivery member and may be spaced apart aroundan outer surface of the elongate body.

A processor of the embodiment of the treatment system may be programmedor otherwise configured (e.g., by execution of instructions stored on anon-transitory computer-readable storage medium) to receive signals fromeach of the temperature-measurement devices, and calculate a peaktemperature of the tissue at a depth based on the received signals. Thepeak temperature may comprise an extreme temperature (e.g., a peak or avalley/trough temperature, a hot or a cold temperature, a positive peakor a negative peak).

According to some embodiments, the processor is configured to calculatethe peak temperature of the tissue at a depth by comparing individualtemperature measurements determined from the received signals to eachother. In some embodiments, the processor is configured to adjust one ormore treatment parameters based on the calculated peak temperature,including duration of treatment, power of energy, target temperature,and maximum temperature.

According to some embodiments, the processor is configured to generatean output to automatically terminate delivery of energy if thecalculated peak temperature exceeds a threshold temperature or togenerate an alert to cause a user to manually terminate energy delivery.In some embodiments, the processor is configured to cause anidentification of the calculated peak temperature to be output to adisplay (e.g., using a color, textual information, and/or numericalinformation).

In accordance with several embodiments, a treatment system comprises amedical instrument (e.g., ablation catheter) comprising an elongate bodycomprising a proximal end and a distal end, an energy delivery memberpositioned at the distal end of the elongate body. In one embodiment,the energy delivery member (e.g., electrode) is configured to contacttissue of a subject and to deliver energy (e.g., ablative energy) to thetissue. The medical instrument comprises a first plurality oftemperature-measurement devices positioned within separate openings orapertures formed in the energy delivery member, and a second pluralityof temperature-measurement devices positioned proximal to the energydelivery member along the elongate body. The first plurality oftemperature-measurement devices may be thermally insulated from theelectrode and spaced apart from each other and the second plurality oftemperature-measurement devices may be thermally insulated from theelectrode. In one embodiment, the second plurality oftemperature-measurement devices is spaced apart around an outer surfaceof the elongate body. The treatment system may also comprise a processorthat is programmed or otherwise configured (e.g., by execution ofinstructions stored on a non-transitory computer-readable storagemedium) to receive signals from each of the temperature-measurementdevices and determine an estimated location of a peak temperature zoneat a depth within the tissue based, at least in part, on the receivedsignals. In some embodiments, the processor determines individualtemperature measurements based on the received signals and compares themto determine the estimated location of the peak temperature. Theprocessor may be configured to adjust one or more treatment parametersbased on the estimated location, including duration, power, targettemperature, and maximum temperature. The processor may also beconfigured to cause an identification of the estimated location to beoutput to a display. The output may comprise alphanumeric informationand/or one or more graphical images indicative of the estimated locationof the peak temperature zone.

In accordance with several embodiments, a method of determining a peaktemperature of tissue being ablated at a depth from a surface of thetissue may comprise receiving signals indicative of temperature from afirst plurality of temperature sensors positioned at a distal end of anablation catheter. In one embodiment, each of the first plurality oftemperature sensors is spaced apart around the distal end of theablation catheter. The method also comprises receiving signalsindicative of temperature from a second plurality of temperature sensorspositioned at a distance proximal to the first plurality of temperaturesensors. The method further comprises determining temperaturemeasurements from the signals received from the first plurality oftemperature sensors and the second plurality of temperature sensors andcomparing the determined temperature measurements to each other. In someembodiments, the method comprises applying one or more correctionfactors to one or more of the determined temperature measurements based,at least in part, on the comparison to determine the peak temperature.In one embodiment, the method comprises outputting the determined peaktemperature on a display textually, visually and/or graphically. In oneembodiment, the method comprises adjusting one or more treatment (e.g.,ablation) parameters and/or terminating ablation based on the determinedhotspot temperature. The second plurality of temperature sensors may bespaced apart around a circumference of the ablation catheter or othermedical instrument.

According to some embodiments, a method of determining a location of apeak temperature zone within tissue being ablated comprises receivingsignals indicative of temperature from a first plurality of temperaturesensors positioned at a distal end of an ablation catheter. In oneembodiment, each of the first plurality of temperature sensors is spacedapart around the distal end of the ablation catheter. The methodcomprises receiving signals indicative of temperature from a secondplurality of temperature sensors positioned at a distance proximal tothe first plurality of temperature sensors. The method further comprisesdetermining temperature measurements from the signals received from thefirst plurality of temperature sensors and the second plurality oftemperature sensors and, comparing the determined temperaturemeasurements to each other. The method may comprise determining alocation of a peak temperature zone of a thermal lesion based, at leastin part, on the comparison. In one embodiment, the method comprisesoutputting the determined peak location on a display, textually,visually and/or graphically. In one embodiment, each of the secondplurality of temperature sensors is spaced apart around a circumferenceof the ablation catheter.

According to some embodiments, a method of determining an orientation ofa distal tip of an ablation catheter with respect to tissue in contactwith the distal tip comprises receiving signals indicative oftemperature from a first plurality of temperature sensors positioned ata distal end of an ablation catheter and receiving signals indicative oftemperature from a second plurality of temperature sensors positioned ata distance proximal to the first plurality of temperature sensors. Themethod further comprises determining temperature measurements from thesignals received from the first plurality of temperature sensors and thesecond plurality of temperature sensors and comparing each of thedetermined temperature measurements with each other. The method furthercomprises determining an orientation of a distal tip of an ablationcatheter with respect to tissue in contact with the distal tip based, atleast in part, on the comparison. In one embodiment, the methodcomprises outputting the determined orientation on a display. The outputmay comprise textual information or one or more graphical images. Theembodiments of the methods may also comprise terminating energy deliveryor generating an output (e.g., an alert) to signal to a user that energydelivery should be terminated. In some embodiments, each of the firstplurality of temperature sensors is spaced apart around a distal end ofthe ablation catheter and each of the second plurality of temperaturesensors is spaced apart around a circumference of the ablation catheter.

In accordance with several embodiments, a system for quickly determiningan orientation of an ablation catheter with respect to a target regioncomprises an ablation catheter comprising an elongate body having aplurality of temperature-measurement devices distributed along a distalend of the elongate body and at least one electrode member positioned atthe distal end of the elongate body, an energy source configured toapply ablative energy to the electrode member sufficient to ablatetarget tissue and at least one processing device. The at least oneprocessing device is configured to, upon execution of specificinstructions stored on a computer-readable medium, determine anorientation of a contact surface of the at least one electrode memberwith respect to the target tissue based on a first set of orientationcriteria at a plurality of time points over a first time period.

The contact surface of the at least one electrode member may be an outerdistal surface of the at least one electrode member (for example a tipelectrode member having a planar or rounded outer distal surface). Insome embodiments, the at least one electrode member is a distalelectrode member of a combination electrode assembly configured forhigh-resolution mapping and radiofrequency energy delivery, thecombination electrode assembly comprising the distal electrode memberand a proximal electrode member separated by a gap, such as thecombination electrode assemblies described herein. In some embodiments,the at least one processing device is configured to determine theorientation of the contact surface of the at least one electrode memberwith respect to the target tissue based on a second set of orientationcriteria at a plurality of time points over a second time periodstarting after an end of the first time period. The second set oforientation criteria may be different than the first orientationcriteria. In embodiments involving two sets of orientation criteria, thefirst time period may correspond to a temperature rise phase wheretemperatures are rising and the second time period corresponds to asteady state phase where temperatures remain at a steady peaktemperature without significant deviation. For example, the first timeperiod may be between 1 and 20 seconds, between 5 and 20 seconds,between 5 and 13 seconds, between 3 and 15 seconds, or between 5 and 10seconds after initial application of ablative energy, as well asoverlapping ranges thereof or any value within the ranges. In someembodiments, the plurality of time points over the first time period andthe second time period occur every second; however other frequencies arepossible for both time periods (e.g., every 100 ms, every 500 ms, every1500 ms, every 2 seconds, every 3 seconds, every 4 seconds, every 5seconds). In some embodiments, the frequency of the time points over thesecond period is longer than the frequency of the time points over thefirst period.

In some embodiments, the first set of orientation criteria comprisestime-dependent conditions and/or static conditions and the second set oforientation criteria consists only of static conditions. The first setof orientation criteria in the temperature rise phase may comprisecomparisons of time-based characteristics of temperature responses of atleast two of the plurality of temperature-measurement devices (forexample, rate of change of temperature over a period of time or the timethat it takes to rise to a certain temperature from a startingtemperature). For example, the comparisons of time-based characteristicsof temperature responses may include different comparisons betweentime-based characteristics of temperature responses of a proximal groupof temperature-measurement devices and time-based characteristics oftemperature responses of a distal group of temperature-measurementdevices. The at least one processing device may be configured todetermine an orientation from a plurality of orientation, or alignment,candidates or options based on the comparisons. For example, if theaverage proximal temperature rise is greater than the average distaltemperature rise by a certain factor, this may be an indicator that theelectrode-tissue orientation is oblique. As another example,time-dependent thresholds may be used to help determine orientationduring the temperature rise phase. For example, the maximum proximaltemperature rise can be subtracted from the minimum distal temperaturerise and this value can be compared to a time-dependent threshold. Ifthe threshold is exceeded, that may be an indicator that the orientationis oblique. The second set of orientation criteria may comprisecomparisons of temperature measurement values of at least two of theplurality of temperature-measurement devices.

The first set of orientation criteria and the second set of orientationcriteria may both involve first testing for a first orientation and ifthe orientation for the first orientation are not satisfied then testingfor a second orientation. If the orientation criteria for the secondorientation are not met, then the at least one processing device maydetermine that the ablation catheter is in a third orientation bydefault if there are only three orientation options. The first set oforientation criteria and the second set of orientation criteria may bothinvolve testing for the orientations in the same order (e.g., oblique,then parallel, then perpendicular) or different orders. The orientationcriteria can vary depending on the order of testing of the orientationoptions. In some embodiments, temperatures may constantly increaseduring a desired time period and so only one set of orientation criteriaare used.

In accordance with several embodiments, a system for determining anorientation of an ablation catheter with respect to a target regioncomprises an ablation catheter comprising an elongate body having aplurality of temperature-measurement devices distributed along a distalend of the elongate body, an energy source configured to apply ablativeenergy sufficient to ablate target tissue to at least one energydelivery member positioned along the distal end of the ablationcatheter; and at least one processing device. The at least oneprocessing device is configured to, upon execution of specificinstructions stored on a computer-readable medium: obtain temperaturemeasurements from each of the plurality of temperature-measurementdevices at a plurality of time points; at each time point, determine atime-based characteristic of a temperature response for each of theplurality of temperature-measurement devices from the obtainedtemperature measurements; and at each time point, determine anorientation of the distal end of the elongate body from one of aplurality of orientation options based, at least in part, on acomparison of the time-based characteristics of the temperatureresponses for at least two of the plurality of temperature-measurementdevices.

The time-based characteristic of the temperature response may be a rateof change of temperature measurement values between a current time pointand a previous time point or the time elapsed between a startingtemperature value and a predefined or predetermined increasedtemperature value. In some embodiments, time-based characteristic of thetemperature response is a difference between temperature measurementvalues at a current time point and a previous time point. In someembodiments, the plurality of time points are spaced apart at regulartime intervals (e.g., every second). The temperature measurement valuesmay be moving average values. In some embodiments, the temperaturemeasurement value at a previous time point is a starting temperaturevalue obtained within five seconds after the ablative energy isinitially applied by the energy source; however times other than fiveseconds may be used (e.g., within ten seconds, within eight seconds,within six seconds, within four seconds, within three seconds, withintwo seconds, at or within one second). The starting temperature valuemay be an average of temperature values obtained over a period of time(for example, an average of temperature values obtained every 100 msfrom 0 to 1 second after initiation of energy delivery).

In various embodiments, the plurality of temperature-measurement devicesconsists of two spaced-apart groups of temperature-measurement devices.In one embodiment, the temperature-measurement devices consists of sixthermocouples. The six thermocouples may comprise a first group of threeco-planar thermocouples and a second group of three co-planarthermocouples spaced proximal to the first group of three thermocouples.Other numbers of temperature-measurement devices may be used as desiredand/or required.

In several embodiments, an initial orientation is advantageouslydetermined quickly after application of ablative energy by the energysource (e.g., less than 20 seconds, less than 15 seconds, less than 10seconds, less than 5 seconds). In accordance with several embodiments,the orientation may be determined quickly because the comparisons of thetemperature responses of the temperature-measurement devices are basedon rate of change rather than the spread or differences in values afterreaching a steady state. The plurality of orientation options maycomprise two or three orientations. If two orientation options arepossible, the options may consist of a parallel orientation and aperpendicular orientation. If three orientation options are possible,the options may consist of a parallel orientation, a perpendicularorientation and an oblique (or angled) orientation. In embodimentsinvolving three orientation options, the at least one processing deviceis configured to first determine whether the orientation is an obliqueorientation based on orientation criteria defined for the obliqueorientation. If the oblique orientation criteria are satisfied, theorientation is determined to be oblique. If the oblique orientationcriteria are not satisfied, then the at least one processing device isthen configured to determine whether the orientation is in a parallelorientation based on orientation criteria defined for the parallelorientation. If the parallel orientation criteria are satisfied, theorientation is determined to be parallel. If the parallel orientationcriteria are not met, then the at least one processing device determinesthat the ablation catheter must be in a perpendicular orientation bydefault. Other orders may be used. For example, a perpendicular orparallel condition could be tested for first if only two orientationoptions are possible.

In accordance with several embodiments, the at least one processingdevice is configured to generate an output indicative of the determinedorientation The output may comprise a graphical icon of an electrode inthe determined orientation and/or other visual indicator identifying thedetermined orientation from the plurality of orientation options. Forexample, the output may comprise a graphical user interface thatincludes three radio buttons, each accompanied by a textual label of arespective one of the plurality of orientation options and the visualindicator may indicate or mark the radio button corresponding to thedetermined orientation.

The orientation criteria may comprise one or more of the following: acomparison of a relationship between an average rate of change oftemperature measurement values of the first plurality oftemperature-measurement devices and an average rate of change oftemperature measurement values of the second plurality oftemperature-measurement devices, a comparison of a relationship betweena maximum rate of change of temperature measurement values of the firstplurality of temperature-measurement devices and a maximum rate ofchange of temperature measurement values of the second plurality oftemperature-measurement devices, a comparison of a relationship betweena maximum rate of change of temperature measurement values of the firstplurality of temperature-measurement devices and a minimum rate ofchange of temperature measurement values of the second plurality oftemperature-measurement devices, a comparison of a relationship betweena minimum rate of change of temperature measurement values of the firstplurality of temperature-measurement devices and a maximum rate ofchange of temperature measurement values of the second plurality oftemperature-measurement devices, a comparison of a rate of change oftemperature measurement values from a previous time point until thecurrent time point between at least two of the first plurality oftemperature-measurement devices, and/or a comparison of a rate of changeof temperature measurement values from a previous time point until thecurrent time point between at least two of the second plurality oftemperature-measurement devices.

In accordance with several embodiments, a method of determining anorientation of a distal end of an ablation catheter with respect to atarget region comprises receiving signals indicative of temperature froma plurality of temperature sensors distributed along a distal end of anablation catheter at a plurality of time points over a period of time,determining temperature measurement values at each of the plurality oftime points for each of the plurality of temperature sensors,calculating a rate of change between the determined temperature valuesat each of the plurality of time points and a starting temperature valuefor each of the plurality of temperature sensors, and, at each timepoint of the plurality of time points, determining an orientation of thedistal end of the ablation catheter relative to a target surface basedon a comparison of the calculated rate of change of at least two of theplurality of temperature sensors.

Determining temperature measurement values at each of the plurality oftime points for each of the plurality of temperature sensors comprisescalculating a moving average value at each of the plurality of timepoints based on a current temperature measurement value and one or moreprevious temperature measurement values in some embodiments. Calculatingthe rate of change between the determined temperature values at each ofthe plurality of time points and the starting temperature value for eachof the plurality of temperature sensors may comprise subtracting thestarting temperature value from the moving average value and dividing bythe time elapsed from the start of the period of time to the currenttime point. In some embodiments, the starting temperature value may bedetermined by receiving signals indicative of temperature from aplurality of temperature sensors distributed along a distal end of anablation catheter at a first plurality of time points in a first periodof time, determining temperature measurement values at each of the firstplurality of time points for each of the plurality of temperaturesensors and then calculating a starting temperature value for each ofthe plurality of temperature sensors based on the determined temperaturemeasurement values.

In some embodiments, the plurality of temperature sensors comprises afirst plurality of temperature sensors (e.g., a first co-planar group ofthree thermocouples or thermistors) positioned at a distal tip of theablation catheter and a second plurality of temperature sensors (e.g., asecond co-planar group of three thermocouples or thermistors) positionedat a distance proximal to the first plurality of temperature sensors. Insome embodiments, determining the orientation of the distal end of theablation catheter relative to the target surface based on a comparisonof the calculated rates of change of at least two of the plurality oftemperature sensors comprises determining whether the calculated ratesof change satisfy one or more orientation criteria of a respectiveorientation (e.g., oblique, parallel or perpendicular). The orientationcriteria may be different for each of the orientation options. At leastsome of the orientation criteria are time-dependent. In accordance withseveral embodiments, the orientation criteria are empirically determinedbased on previous data.

In accordance with several embodiments, a method of determining anorientation of a distal end of an ablation catheter with respect to atarget region comprises receiving signals indicative of temperature froma plurality of temperature sensors distributed along a distal end of anablation catheter at a plurality of time points over a period of time,determining temperature measurement values at each of the plurality oftime points for each of the plurality of temperature sensors,determining a characteristic of a temperature response at each of theplurality of time points for each of the plurality of temperaturesensors, and, at each time point of the plurality of time points,determining an orientation of the distal end of the ablation catheterrelative to a target surface based on a comparison of thecharacteristics of the temperature responses of at least two of theplurality of temperature sensors. The characteristic of the temperatureresponse may be a rate of change of the temperature or a differencebetween a temperature measurement value obtained at a current time pointand a temperature measurement value obtained at a previous time point orthe time it takes to rise from a starting temperature value to apredetermined increased temperature value.

In accordance with several embodiments, a method of determining anorientation of a distal end of an ablation catheter with respect to atarget region comprises receiving signals indicative of temperature froma plurality of temperature sensors distributed along a distal end of anablation catheter at a first plurality of time points over a firstperiod of time; determining temperature measurement values at each ofthe first plurality of time points for each of the plurality oftemperature sensors; at each time point of the first plurality of timepoints, determining an orientation of the distal end of the ablationcatheter relative to a target surface based on a first set oforientation criteria applied to the determined temperature measurementvalues; receiving signals indicative of temperature from the pluralityof temperature sensors at a second plurality of time points over asecond period of time after the first period of time; determiningtemperature measurement values at each of the second plurality of timepoints for each of the plurality of temperature sensors; and, at eachtime point of the second plurality of time points, determining anorientation of the distal end of the ablation catheter relative to atarget surface based on a second set of orientation criteria applied tothe determined temperature measurement values. In several embodiments,the second set of orientation criteria is different than the first setof orientation criteria. For example, the first set of orientationcriteria may comprise comparisons of time-based characteristics oftemperature responses of at least two of the plurality of temperaturesensors and the second set of orientation criteria comprises comparisonsof temperature measurement values of at least two of the plurality oftemperature sensors. The first period of time may correspond to atemperature rise phase and the second period of time may correspond to asteady state phase. The first set of orientation criteria and the secondset of orientation criteria may be empirically determined.

In accordance with several embodiments, a method of determining anorientation of a distal end of an ablation catheter with respect to atarget region comprises receiving signals indicative of temperature froma plurality of temperature sensors distributed along a distal end of anablation catheter at a first plurality of time points in a first periodof time; determining temperature measurement values at each of the firstplurality of time points for each of the plurality of temperaturesensors; calculating a starting temperature value for each of theplurality of temperature sensors based on the determined temperaturemeasurement values; receiving signals indicative of temperature from theplurality of temperature sensors at a second plurality of time points ina second period of time after the first period of time; determiningtemperature measurement values at each of the second plurality of timepoints for each of the plurality of temperature sensors; calculating arate of change between the determined temperature values at each of thesecond plurality of time points and a starting temperature value foreach of the plurality of temperature sensors; and, at each time point ofthe second plurality of time points, determining an orientation of thedistal end of the ablation catheter relative to a target surface basedon a comparison of the calculated rate of change of at least two of theplurality of temperature sensors. In some embodiments, the methodfurther comprises receiving signals indicative of temperature from theplurality of temperature sensors during a third period of time after thesecond period of time, determining temperature measurement values foreach of the plurality of temperature sensors and determining anorientation of the distal end of the ablation catheter relative to thetarget surface based on a comparison of the temperature measurementvalues of at least two of the plurality of temperature sensors.

In accordance with several embodiments, a system comprises at least onesignal source configured to deliver at least a first frequency and asecond frequency to a pair of electrodes or electrode portions of acombination electrode or electrode assembly. The system also comprises aprocessing device configured to: obtain impedance measurements while thefirst frequency and the second frequency are being applied to the pairof electrodes by the signal source, process the electrical (e.g.,voltage, current, impedance) measurements obtained at the firstfrequency and the second frequency, and determine whether the pair ofelectrodes is in contact with tissue based on said processing of theelectrical (e.g., impedance) measurements. The pair of electrodes may bepositioned along a medical instrument (e.g., at a distal end portion ofan ablation catheter). The pair of electrodes may compriseradiofrequency electrodes and the at least one signal source maycomprise one, two or more sources of radiofrequency energy.

The signal source may comprise a first signal source configured togenerate, deliver or apply signals to the pair of electrodes having afrequency configured for tissue ablation and a second signal sourceconfigured to generate, deliver or apply signals to the pair ofelectrodes having frequencies adapted for contact sensing and/or tissuetype determination (e.g., whether the tissue is ablated or stillviable). The first and second signal sources may be integrated within anenergy delivery module (e.g., RF generator) or within an elongate bodyor handle of a medical instrument (e.g., ablation catheter). In someembodiments, the second signal source is within a contact sensingsubsystem, which may be a distinct and separate component from theenergy delivery module and medical instrument or integrated within theenergy delivery module or medical instrument. In one embodiment, onlyone signal source capable of applying signals having frequencies adaptedfor ablation or other treatment and signals having frequencies adaptedfor contact sensing or tissue type determination functions is used. Thefrequencies adapted for contact sensing or tissue type determination maybe within the treatment frequency range or outside the treatmentfrequency range. By way of example, in one non-limiting embodiment, thesystem comprises an energy source configured to generate, deliver orapply signals to at least a pair of electrode members (and also to aground pad or reference electrode) to deliver energy having a frequencyconfigured for tissue ablation or other treatment and a signal sourceconfigured to generate, deliver or apply signals to the pair ofelectrode members (and not to a ground pad or reference electrode)having frequencies adapted for contact sensing and/or tissue typedetermination (e.g., whether the tissue is ablated or still viable). Thesignals generated by the signal source may comprise constant current ACexcitation signals or AC voltage excitation signals. The excitationsignals may advantageously be outside the frequency range of theablative frequencies and/or electrogram mapping frequencies. The energysource and the signal source may both be integrated within an energydelivery module (e.g., RF generator) or one of the sources (e.g., thesignal source) may be incorporated within an elongate body or handle ofa medical instrument (e.g., ablation catheter). In some embodiments, thesignal source is within a contact sensing subsystem, which may be adistinct and separate component from the energy delivery module andmedical instrument or integrated within the energy delivery module ormedical instrument. In some embodiments, a single source configured forapplying signals having frequencies adapted for ablation or othertreatment and configured for applying signals having frequencies adaptedfor contact sensing or tissue type determination functions is used.Signals having the treatment frequencies (for example, frequenciesadapted for ablation of cardiac tissue) may also be delivered to aground pad or reference electrode.

In some embodiments, the system consists essentially of or comprises amedical instrument (e.g., an energy delivery device), one or more energysources, one or more signal sources and one or more processing devices.The medical instrument (e.g., energy delivery catheter) may comprise anelongate body having a proximal end and a distal end and a pair ofelectrodes or electrode portions (e.g., a combination, or composite,such as a split-tip, electrode assembly) positioned at the distal end ofthe elongate body. In one embodiment, the pair of electrodes comprisesor consists essentially of a first electrode positioned on the elongatebody and a second electrode positioned adjacent (e.g., proximal of) thefirst electrode. The first electrode and the second electrode may beconfigured to contact tissue of a subject and provide energy to thetissue to heat (e.g., ablate or otherwise treat) the tissue at a depthfrom the surface of the tissue. In one embodiment, the pair ofelectrodes comprises an electrically insulating gap positioned betweenthe first electrode and the second electrode, the electricallyinsulating gap comprising a gap width separating the first and secondelectrodes. A separator (e.g., a capacitor or insulation material) maybe positioned within the electrically insulating gap.

The one or more signal sources may be configured to deliver signals overa range of frequencies (e.g., frequencies within a radiofrequencyrange). In some embodiments, the processing device is configured toexecute specific program instructions stored on a non-transitorycomputer-readable storage medium to: obtain impedance or otherelectrical measurements while different frequencies of energy within therange of frequencies are being applied to the pair of electrodes by asignal source, process the impedance or other electrical measurementsobtained at the first frequency and the second frequency, and determinewhether at least one of (e.g., the distal-most electrode) the pair ofelectrodes is in contact with tissue based on said processing of theimpedance or other electrical measurements. In accordance with severalembodiments, the impedance measurements constitute bipolar contactimpedance between the pair of electrodes or between the electrodemembers of a combination electrode assembly and not the impedancebetween an electrode and target tissue. In accordance with severalembodiments, the impedance or other electrical measurements do notinvolve passing current to one or more patch or reference electrodespositioned at a location external to the medical instrument or at alocation remote from the target tissue (for example, at a location onthe skin of a patient at the neck, torso and/or leg).

In some embodiments, the medical instrument consists essentially of orcomprises a radiofrequency ablation catheter and the first and secondelectrodes or electrode portions comprise radiofrequency electrodes. Thesignal source(s) may comprise a radiofrequency (RF) generator. In oneembodiment, the range of frequencies that is delivered by the signalsource(s) (e.g., of a contact sensing subsystem) comprises at least arange between 1 kHz and 5 MHz (e.g., between 5 kHz and 1000 kHz, between10 kHz and 500 kHz, between 5 kHz and 800 kHz, between 20 kHz and 800kHz, between 50 kHz and 5 MHz, between 100 kHz and 1000 kHz, andoverlapping ranges thereof). The signal source(s) may also be configuredto deliver frequencies below and above this range. The frequencies maybe at least greater than five times or at least greater than ten timesthe electrogram mapping frequencies so as not to interfere withhigh-resolution mapping images or functions obtained by the first andsecond electrodes or electrode portions. In one embodiment, thedifferent frequencies at which impedance measurements are obtainedconsists only of two discrete frequencies. In another embodiment, thedifferent frequencies comprise two or more discrete frequencies. In someembodiments, the processing device is configured to obtain impedancemeasurements while a full sweep of frequencies from a minimum frequencyto a maximum frequency of the range of frequencies is applied to thepair of electrodes or electrode portions. As one example, the range offrequencies is between 5 kHz and 1000 kHz. The second frequency may bedifferent from (e.g., higher or lower than) the first frequency. Inaccordance with several embodiments, the frequencies used for contactsensing or determination are outside (for example, below) the frequencyrange of the ablative frequencies.

The system may comprise an ablative energy source (e.g., signal sourcesuch as an RF generator) configured to deliver signals to the pair ofelectrodes (and possibly also to a ground pad or reference electrode) togenerate energy sufficient to ablate or otherwise treat tissue (such ascardiac tissue). In one embodiment, the processing device is configuredto adjust one or more energy delivery parameters of the ablative energybased on a determination of whether at least one of the pair ofelectrodes is in contact with tissue and/or is configured to terminateenergy delivery based on a determination of whether at least one of thepair of electrodes is in contact with tissue or that contact has beenlost. In some embodiments, the ablative energy source and the at leastone signal source comprise a single source. In other embodiments, thesignal source comprises a first source and the ablative energy sourcecomprises a second source that is separate and distinct from the firstsource. In some embodiments, the processing is performed in the timedomain. In some embodiments, the processing is performed in thefrequency domain. Portions of the processing may be performed in boththe time domain and the frequency domain.

In some embodiments, the processing device is configured to executespecific program instructions stored on a non-transitorycomputer-readable storage medium to generate an output indicative ofcontact. The processing device may be configured to cause the generatedoutput to be displayed on a display (for example an LCD or LED monitor)in communication with the processing device. In various embodiments, theoutput comprises textual information, quantitative information (e.g.,numeric information, binary assessment of whether contact exists or not)and/or a qualitative information (e.g., color or other informationindicative of a level of contact).

In accordance with several embodiments, a system comprises a signalsource configured to deliver signals having a range of frequencies and aprocessing device configured to execute specific program instructionsstored on a non-transitory computer-readable storage medium to: obtainimpedance (e.g., bipolar contact impedance) or other electricalmeasurements while different frequencies of energy are being applied toa pair of electrodes (e.g., combination electrode, or composite (such asa split-tip), electrode assembly) by the signal source, compare theimpedance measurements obtained at the different frequencies of energy;and determine whether or not tissue in contact with at least one of thepair of electrodes has been ablated. In some embodiments, the range offrequencies over which contact determination is made is between 5 kHzand 1000 kHz. The different frequencies consist of two discretefrequencies in one embodiment or may comprise two or more discretefrequencies in other embodiments. The processing device may beconfigured to obtain impedance measurements while a full sweep offrequencies from a minimum frequency to a maximum frequency of the rangeof frequencies (e.g., 5 kHz to 1000 kHz) is applied to the pair ofelectrodes. In some embodiments, one component of an impedancemeasurement (e.g., impedance magnitude) is obtained at a first frequencyand a second component of a different impedance measurement (e.g., phaseangle) is obtained at a second frequency. A comparison (e.g., derivativeof impedance versus frequency, delta or slope of impedance vs.frequency) of impedance magnitude measurements between the pair ofelectrodes at two or more different frequencies may also be obtained. Aweighted combination of various impedance measurements at two or moredifferent frequencies may be calculated by the processing device andused by the processing device to determine an overall contact level orstate. The impedance measurements may be obtained directly or may becalculated based on electrical parameter measurements, such as voltageand/or current measurements. In accordance with several embodiments, theimpedance measurements comprise bipolar impedance measurements.

In some embodiments, the processing device is configured to executespecific program instructions stored on a non-transitorycomputer-readable storage medium to generate an output indicative oftissue type based on the determination of whether or not tissue incontact with at least one of the pair of electrodes has been ablated.The processing device may be configured to cause the generated output tobe displayed on a display in communication with the processing device.The output may comprise one or more of textual information, a color orother qualitative information, and numerical information. In variousembodiments, the processing device is configured to adjust one or moreenergy delivery parameters based on the determination of whether thetissue in contact with the pair of electrodes has been ablated and/or isconfigured to terminate energy delivery based on the determination ofwhether tissue in contact with the pair of electrodes has been ablated.

In accordance with several embodiments, a system for determining whethera medical instrument is in contact with tissue based, at least in part,on impedance measurements comprises a signal source configured todeliver signals having different frequencies to a pair of electrodes ofa medical instrument and a processing device configured to process aresulting waveform that formulates across the pair of electrodes toobtain impedance measurements at a first frequency and a secondfrequency and determine a ratio between the magnitude of the impedanceat the second frequency and the first frequency. If the determined ratiois below a predetermined threshold indicative of contact, the processingdevice is configured, upon execution of stored instructions on acomputer-readable medium, to generate a first output indicative ofcontact. If the determined ratio is above the predetermined threshold,the processing device is configured to, upon execution of storedinstructions on a computer-readable medium, generate a second outputindicative of no contact. In one embodiment, the signal source comprisesa radiofrequency energy source. The first and second frequencies may bebetween 5 kHz and 1000 kHz. In some embodiments, the signal source isconfigured to generate signals having a frequency adapted for tissueablation. In other embodiments, the system comprises a second signalsource (or an ablative energy source) configured to generate signalshaving a frequency adapted for tissue ablation. The frequency adaptedfor tissue ablation may be between 400 kHz and 600 kHz (e.g., 400 kHz,450 kHz, 460 kHz, 480 kHz, 500 kHz, 550 kHz, 600 kHz, 400 kHz-500 kHz,450 kHz-550 kHz, 500 kHz-600 kHz, or overlapping ranges thereof). Invarious embodiments, the predetermined threshold is a value between 0.5and 0.9. Processing the waveforms may comprise obtaining voltage and/orcurrent measurements and calculating impedance measurements based on thevoltage and/or current measurements or directly obtaining impedancemeasurements.

A method of determining whether a medical instrument is in contact witha target region (e.g., tissue) based, at least in part, on electricalmeasurements (e.g., impedance measurements), may comprise applyingsignals having a first frequency and a second frequency to a pair ofelectrodes or electrode portions of the medical instrument, processing aresulting waveform to obtain impedance measurements at the firstfrequency and the second frequency, and determining a ratio between themagnitude of the impedance at the second frequency and the firstfrequency. If the determined ratio is below a predetermined thresholdindicative of contact, the method comprises generating a first outputindicative of contact. If the determined ratio is above thepredetermined threshold, the method comprises generating a second outputindicative of no contact. The method may further comprise applying asignal adapted to cause ablative energy to be delivered by the pair ofelectrodes or electrode portions sufficient to ablate the target region(for example, cardiac tissue or other body tissue).

In accordance with several embodiments, a system for determining acontact state of a distal end portion of a medical instrument with atarget region (e.g., tissue) based, at least in part, on electricalmeasurements comprises a signal source configured to generate at leastone signal having a first frequency and a second frequency to be appliedto a pair of electrode members of a combination electrode assembly. Thesignal source may be a component of a contact sensing or detectionsubsystem or an energy delivery module, such as a radiofrequencygenerator. The system also comprises a processor or other computingdevice configured to, upon execution of specific program instructionsstored in memory or a non-transitory computer-readable storage medium,cause the signal source to generate and apply the at least one signal tothe pair of electrode members. The signal may be a single multi-tonewaveform or signal or multiple waveforms or signals having a singlefrequency.

The processor may be configured to process a resulting waveform thatformulates across the pair of electrode members to obtain a firstelectrical measurement at the first frequency and to process theresulting waveform that formulates across the pair of electrode membersto obtain a second electrical measurement at the second frequency of theplurality of frequencies. The processor is further configured to:determine an impedance magnitude based on the first electricalmeasurement (e.g., voltage and/or current measurement), determine animpedance magnitude and a phase based on the second electricalmeasurement, and calculate a contact indication value indicative of astate of contact between the distal end portion of the medicalinstrument and the target region based on a criterion combining theimpedance magnitude based on the first electrical measurement, a ratioof the impedance magnitudes based on the first electrical measurementand the second electrical measurement, and the phase based on the secondelectrical measurement. The first and second electrical measurements maycomprise voltage and/or current measurements or direct impedancemeasurements between the pair of electrode members. In some embodiments,the first and second electrical measurements do not comprise directmeasurements of electrical parameters or a degree of coupling between anelectrode and tissue but are measurements between two electrode members.Impedance measurements may be calculated based on the voltage and/orcurrent measurements or may be directly obtained or measured by aninstrument or device configured to output impedance measurements. Theimpedance measurements may comprise complex impedance measurementscomposed of real and imaginary components (for example, impedancemagnitude and phase angle measurements or resistance and reactancemeasurements). In accordance with several embodiments, the impedancemeasurements comprise bipolar contact impedance measurements between thetwo electrode members.

In some embodiments, the criterion comprises a weighted combination ofthe impedance magnitude based on the first electrical measurement, aratio of the impedance magnitudes based on the first and secondelectrical measurements, and the phase based on the second electricalmeasurement. In some embodiments, the criterion comprises an if-thencase conditional criterion, such as described in connection with FIGS.11 and 11A. In various embodiments, only one impedance measurement orcalculation (e.g., only impedance magnitude, only slope betweenimpedance magnitude values, or only phase) or only two types ofimpedance measurements or calculations are used to determine the contactstate.

In accordance with several embodiments, a system for determining whethera medical instrument is in contact with a target region (e.g., tissue)based, at least in part, on impedance measurements consists essentiallyof or comprises a signal source configured to generate one or moresignals having a first frequency and a second frequency to a pair ofelectrodes (e.g., positioned at a distal end of a medical instrument,catheter or probe) and a processing device configured to executespecific program instructions stored on a non-transitorycomputer-readable storage medium to process a resulting waveform thatformulates across the pair of electrodes to obtain impedancemeasurements at the first frequency and the second frequency. If theimpedance magnitude at the first and/or second frequency is above apredetermined threshold indicative of contact, the processing device isconfigured to, upon execution of stored instructions on thecomputer-readable storage medium, generate a first output indicative ofcontact. If the impedance magnitude at the first and/or second frequencyis below a predetermined threshold indicative of no contact, theprocessing device is configured to, upon execution of storedinstructions on the computer-readable storage medium, generate a secondoutput indicative of no contact. Processing the waveforms may compriseobtaining voltage and/or current measurements and calculating impedancemeasurements based on the voltage and/or current measurements ordirectly obtaining impedance measurements.

A method of determining whether a medical instrument is in contact witha target region (e.g., tissue) based, at least in part, on impedancemeasurements comprises delivering at least one signal having a firstfrequency and a second frequency (e.g., a multi-tonal waveform) to apair of electrodes or electrode portions and processing a resultingwaveform that formulates across the pair of electrodes to obtainimpedance measurements at the first frequency and the second frequency.If the impedance magnitude at the first frequency and/or secondfrequency is above a predetermined threshold indicative of contact, themethod comprises generating a first output indicative of contact. If theimpedance magnitude at the first frequency and/or second frequency isbelow a predetermined threshold indicative of no contact, the methodcomprises generating a second output indicative of no contact. Themethod may further comprise applying a signal adapted to cause ablativeenergy to be delivered by the pair of electrodes or electrode portionssufficient to ablate or otherwise treat cardiac or other body tissue.

A method of determining whether a medical instrument is in contact witha target region (e.g., tissue) based, at least in part, on impedancemeasurements may comprise applying a signal comprising a multi-tonewaveform having a first frequency and a second frequency to a pair ofelectrodes, processing the resulting waveform to obtain impedancemeasurements at the first frequency and the second frequency, comparingvalues of the impedance measurements at the first frequency and thesecond frequency to a known impedance of blood or a blood and salinemixture (or other known tissue impedance), comparing values of theimpedance measurements at the first and second frequency to each other;and generating an output indicative of whether or not the medicalinstrument is in contact with tissue based on said comparisons. A systemfor determining whether a medical instrument is in contact with tissuebased, at least in part, on impedance measurements may comprise a signalsource configured to generate a multi-tone waveform or signal having afirst frequency and a second frequency to a pair of electrodes (e.g., ata distal end of a combination electrode (such as a split-tip electrode)catheter); and a processing device. The processing device may beconfigured to, upon execution of stored instructions on acomputer-readable storage medium, process the resulting waveform toobtain impedance measurements at the first frequency and the secondfrequency, compare values of the impedance measurements at the firstfrequency and the second frequency to a known impedance of blood or ablood and saline mixture, compare values of the impedance measurementsat the first and second frequency to each other and/or generate anoutput indicative of whether or not the medical instrument is in contactwith tissue based on said comparisons. The method may further compriseapplying a signal adapted to cause ablative energy to be delivered bythe pair of electrodes or electrode portions sufficient to ablate orotherwise treat cardiac or other body tissue.

In accordance with several embodiments, a method of determining whethera medical instrument comprising a pair of electrodes or electrodeportions is in contact with a target region (e.g., tissue) based, atleast in part, on impedance measurements comprises applying at least onesignal having a plurality of frequencies (e.g., a multi-tonal waveform)to a pair of electrodes of a medical instrument, and processing aresulting waveform that formulates across the pair of electrodes toobtain impedance measurements at a first frequency and a secondfrequency of the plurality of frequencies. If a variation of theimpedance measurements across the range of frequencies has a model whoseparameter values are indicative of contact, the method comprisesgenerating a first output indicative of contact. If the variation of theimpedance measurements across the range of frequencies has a model whoseparameter values are indicative of no contact, the method comprisesgenerating a second output indicative of no contact. The model maycomprise a fitting function or a circuit model such as shown in FIG. 5B.The method may further comprise applying a signal adapted to causeablative energy to be delivered by the pair of electrodes or electrodeportions sufficient to ablate or otherwise treat cardiac or other bodytissue.

A system for determining whether a medical instrument is in contact withtissue based, at least in part, on impedance measurements comprises asignal source configured to generate at least one signal having a firstfrequency and a second frequency to a pair of electrodes and aprocessing device. The processing device may be configured to, uponexecution of stored instructions on a computer-readable storage medium,apply at least one signal having a plurality of frequencies to a pair ofelectrodes of a medical instrument and process a resulting waveform thatformulates across the pair of electrodes to obtain impedancemeasurements at a first frequency and a second frequency of theplurality of frequencies. If a variation of the impedance measurementsacross the range of frequencies follows a model whose parameter valuesare indicative of contact the processor is configured to generate afirst output indicative of contact. If the variation of the impedancemeasurements across the range of frequencies follows a model whoseparameter values are indicative of no contact, the processor isconfigured to generate a second output indicative of no contact.Processing the waveforms to obtain impedance measurements may compriseobtaining voltage and/or current measurements and calculating impedancemeasurements based on the voltage and/or current measurements ordirectly obtaining impedance measurements.

In accordance with several embodiments, a method of determining whethertissue has been ablated by an ablation catheter comprising a pair ofelectrodes is provided. The method comprises applying one or moresignals having a first frequency and a second frequency (e.g., amulti-tonal waveform) to a pair of electrodes along the ablationcatheter and processing a resulting waveform that formulates across thepair of electrodes to obtain impedance measurements at the firstfrequency and the second frequency. The method may comprise assessingabsolute change in the impedance as well as the slope or ratio betweenimpedance. If the first impedance measurement at the first and/or secondfrequency is greater than a known impedance level of blood and if aratio of the second impedance measurement to the first impedancemeasurement is above a predetermined threshold, the method comprisesgenerating a first output indicative of ablated tissue. If the firstimpedance measurement at the first and/or second frequency is greaterthan a known impedance level of blood and if a ratio of the secondimpedance measurement to the first impedance measurement is below apredetermined threshold, the method comprises generating a second outputindicative of viable tissue. Processing the waveforms to obtainimpedance measurements may comprise obtaining voltage and/or currentmeasurements and calculating impedance measurements based on the voltageand/or current measurements or directly obtaining impedancemeasurements. The method may further comprise applying a signal adaptedto cause ablative energy to be delivered by the pair of electrodes orelectrode portions sufficient to ablate or otherwise treat cardiac orother body tissue.

In some embodiments, a phase of the impedance measurements at the firstfrequency and/or second frequency is compared to a known phase responsefor blood or a blood and saline mixture and utilized in conjunction withthe magnitude values of the impedance measurements to generate an outputindicative of whether or not the medical instrument is in contact withtissue. A system for determining whether tissue has been ablated by anablation catheter comprising a pair of electrodes or electrode portionsmay comprise a signal source configured to generate at least one signalhaving a first frequency and a second frequency to a pair of electrodesalong the ablation catheter and a processing device. The processingdevice may be configured to, upon execution of stored instructions on acomputer-readable storage medium, process a resulting waveform thatformulates across the pair of electrodes to obtain impedancemeasurements at the first frequency and the second frequency. If thefirst impedance measurement at the first and/or second frequency isgreater than a known impedance level of blood and if a ratio of thesecond impedance measurement to the first impedance measurement is abovea predetermined threshold, the processing device is configured togenerate a first output indicative of ablated tissue. If a ratio of thesecond impedance measurement to the first impedance measurement is belowa predetermined threshold, the processor is configured to generate asecond output indicative of viable (e.g., unablated) tissue. Processingthe waveforms to obtain impedance measurements may comprise obtainingvoltage and/or current measurements and calculating impedancemeasurements based on the voltage and/or current measurements ordirectly obtaining impedance measurements.

Processing the resulting waveform may comprise applying a transform(e.g., a Fourier transform) to the waveform to obtain the impedancemeasurements. In some embodiments, the first frequency and the secondfrequency are within a range between 5 kHz and 1000 kHz. In oneembodiment, the second frequency is higher than the first frequency. Theimpedance measurements may be obtained simultaneously or sequentially.The second frequency may be at least 20 kHz higher than the firstfrequency. In one embodiment, the first frequency is between 10 kHz and100 kHz (e.g., between 10 KHz and 30 kHz, between 15 kHz and 40 kHz,between 20 kHz and 50 kHz, between 30 kHz and 60 kHz, between 40 kHz and80 kHz, between 50 kHz and 90 kHz, between 60 kHz and 100 kHz,overlapping ranges thereof, 20 kHz or any values from 10 kHz and 100kHz) and the second frequency is between 400 kHz and 1000 kHz (e.g.,between 400 kHz and 600 kHz, between 450 kHz and 750 kHz, between 500kHz and 800 kHz, between 600 kHz and 850 kHz, between 700 kHz and 900kHz, between 800 kHz and 1000 kHz, overlapping ranges thereof, 800 kHz,or any values from 400 kHz to 1000 kHz). The predetermined threshold mayhave a value between 0.5 and 0.9. In some embodiments, generating afirst output and generating a second output further comprises causingthe first output or the second output to be displayed on a display (forexample via one or more display drivers). The output may comprisetextual information, quantitative measurements and/or qualitativeassessments indicative of contact state. In some embodiments, the outputincludes an amount of contact force corresponding to the level ofcontact (e.g., grams of force).

A method of determining whether a medical instrument having a pair ofelectrodes or electrode portions is in contact with a target region(e.g., tissue) based, at least in part, on impedance measurements maycomprise obtaining a first impedance measurement at a first frequencywithin a range of frequencies, obtaining a second impedance measurementat a second frequency within the range of frequencies and obtaining athird impedance measurement at a third frequency within the range offrequencies. If a variation of the impedance measurements across therange of frequencies is above a predetermined threshold indicative ofcontact, the method comprises generating a first output indicative ofcontact. If the variation of the impedance measurements across the rangeof frequencies is below the predetermined threshold, the methodcomprises generating a second output indicative of no contact. Theimpedance measurements may be calculated based on voltage and/or currentmeasurements or may be directly-measured impedance measurements. Themethod may further comprise applying a signal adapted to cause ablativeenergy to be delivered by the pair of electrodes or electrode portionssufficient to ablate or otherwise treat cardiac or other body tissue.

The range of frequencies may be between 5 kHz and 5 MHz (e.g., between 5kHz and 1000 kHz, between 1 MHz and 3 MHz, between 2.5 MHz and 5 MHz, oroverlapping ranges thereof). In one embodiment, the first frequency isbetween 10 kHz and 100 kHz (e.g., between 10 KHz and 30 kHz, between 15kHz and 40 kHz, between 20 kHz and 50 kHz, between 30 kHz and 60 kHz,between 40 kHz and 80 kHz, between 50 kHz and 90 kHz, between 60 kHz and100 kHz, overlapping ranges thereof, 20 kHz or any values from 10 kHzand 100 kHz) and the second frequency is between 400 kHz and 1000 kHz(e.g., between 400 kHz and 600 kHz, between 450 kHz and 750 kHz, between500 kHz and 800 kHz, between 600 kHz and 850 kHz, between 700 kHz and900 kHz, between 800 kHz and 1000 kHz, overlapping ranges thereof, 800kHz, or any values from 400 kHz to 1000 kHz) and the third frequency isbetween 20 kHz and 800 kHz. The predetermined threshold may be a valuebetween 0.5 and 0.9. In some embodiments, generating a first output andgenerating a second output comprises causing the first output or thesecond output to be displayed on a display. The output may comprisetextual information indicative of contact. In one embodiment, the outputcomprises a quantitative measurement and/or qualitative assessment ofcontact.

In some embodiments, the distal end portion of the medical instrumentcomprises a high-resolution electrode assembly comprising a firstelectrode portion and second electrode portion spaced apart andinsulated from the first electrode portion (e.g., a composite electrodeassembly or combination radiofrequency electrode). The control unit maycomprise a contact detection subsystem or module configured to receivesignals from the high-resolution electrode assembly and the control unit(e.g., processor) of the contact detection subsystem or module or aseparate processor may be configured (e.g., specifically programmed withinstructions stored in or on a non-transitory computer-readable medium)to determine a level of contact or a contact state with tissue (e.g.,cardiac tissue) based on the received signals from the high-resolutionelectrode assembly and to modulate the opposition force provided by theopposition force motor based, at least in part, on the determined levelof contact, or the contact state. The control unit may further comprisea power delivery module configured to apply radiofrequency power to thehigh-resolution electrode assembly at a level sufficient to effectablation of tissue in contact with at least a portion of the distal endportion of the medical instrument.

In some embodiments, the control unit (e.g., processor) is configured togenerate output indicative of the level of contact for display on adisplay coupled to the control unit (e.g., via one or more displaydrivers). In various embodiments, the output is based on a contactfunction determined based on one or more criteria combining multipleelectrical parameter measurements (such as voltage measurements, currentmeasurements or impedance measurements). In one embodiment, the contactfunction is determined by summing a weighted combination of impedance(e.g., bipolar impedance) measurements that are directly measured orthat are calculated based on voltage and/or current measurements. In oneembodiment, the contact function is based on one or more if-then caseconditional criteria. In one embodiment, the impedance measurementscomprise one or more of an impedance magnitude determined by the contactdetection subsystem at a first frequency, a ratio of impedancemagnitudes at the first frequency and a second frequency and a phase ofa complex impedance measurement at the second frequency. The secondfrequency may be higher than the first frequency (e.g., at least 20 kHzhigher than the first frequency). In some embodiments, the firstfrequency and the second frequency are between 5 kHz and 1000 kHz. Inone embodiment, the first frequency is between 10 kHz and 100 kHz (e.g.,between 10 KHz and 30 kHz, between 15 kHz and 40 kHz, between 20 kHz and50 kHz, between 30 kHz and 60 kHz, between 40 kHz and 80 kHz, between 50kHz and 90 kHz, between 60 kHz and 100 kHz, overlapping ranges thereof,20 kHz or any values from 10 kHz and 100 kHz) and the second frequencyis between 400 kHz and 1000 kHz (e.g., between 400 kHz and 600 kHz,between 450 kHz and 750 kHz, between 500 kHz and 800 kHz, between 600kHz and 850 kHz, between 700 kHz and 900 kHz, between 800 kHz and 1000kHz, overlapping ranges thereof, 800 kHz, or any values from 400 kHz to1000 kHz); however, other frequencies may be used as desired and/orrequired. In some embodiments, the frequencies at which impedancemeasurements are obtained are outside treatment (e.g., ablation)frequency ranges. In some embodiments, filters (such as bandpassfilters) are used to isolate the treatment frequency ranges from theimpedance measurement frequency ranges.

In some embodiments, the handle of the medical instrument furthercomprises a motion detection element (e.g., at least one of anaccelerometer and a gyroscope). In some embodiments, the first motor isconfigured to be actuated only when the motion detection element isdetecting motion of the handle.

In accordance with several embodiments, a method of determining acontact state of a distal end portion of a medical instrument with atarget region, for example, tissue, comprises applying at least onesignal having a plurality of frequencies to a pair of electrodes orelectrode portions of a combination electrode assembly positioned alonga distal end portion of a medical instrument. The method comprisesprocessing a resulting waveform that formulates across the pair ofelectrodes to obtain a first impedance measurement at a first frequencyof the plurality of frequencies and processing the resulting waveformthat formulates across the pair of electrodes to obtain a secondimpedance measurement at a second frequency of the plurality offrequencies. The method further comprises determining a magnitude of thefirst impedance measurement, determining a magnitude and a phase of thesecond impedance measurement and applying a contact function (e.g., viaexecution of a computer program stored on a non-transitory computerstorage medium) to calculate a contact indication value indicative of astate of contact between the distal end portion of the medicalinstrument and the target region (e.g., cardiac tissue). The contactfunction may be determined by summing a weighted combination of themagnitude of the first impedance measurement, a ratio of the magnitudesof the first impedance measurement and the second impedance measurement,and the phase of the second impedance measurement. In variousembodiments, the first frequency and the second frequency are different.In one embodiment, the second frequency is higher than the firstfrequency.

The method may further comprise generating output corresponding to thecontact indication value for display on a display monitor (e.g., via oneor more display drivers). In some embodiments, the output comprises aqualitative and/or a quantitative output. The output may comprise anumerical value between 0 and 1 or between 0 and 1.5, with values above1 indicating excessive contact. In some embodiments, the outputcomprises a percentage value or a number corresponding to an amount ofcontact force (e.g., grams of contact force). The output may comprise acolor and/or pattern indicative of the contact state and/or one or moreof a gauge, a bar, or a scale. The method may further comprise applyinga signal adapted to cause ablative energy to be delivered by the pair ofelectrodes or electrode portions sufficient to ablate or otherwise treatcardiac or other body tissue.

In accordance with several embodiments, a system for determining acontact state of a distal end portion of a medical instrument with atarget region (e.g., tissue, based, at least in part, on electricalparameter measurements consists essentially of or comprises a signalsource configured to generate at least one signal having a firstfrequency and a second frequency to be applied to a pair of electrodemembers of a combination electrode assembly (e.g., two electrode membersseparated by a gap). The system also consists essentially of orcomprises a processing device configured to (a) cause the signal sourceto generate and apply the at least one signal to the pair of electrodemembers, (b) process a resulting waveform that formulates across thepair of electrode members to obtain a first electrical measurement atthe first frequency, (c) process the resulting waveform that formulatesacross the pair of electrode members to obtain a second electricalmeasurement at the second frequency of the plurality of frequencies, (d)determine an impedance magnitude based on the first electricalmeasurement, (e) determine an impedance magnitude and a phase based onthe second electrical measurement, and (f) calculate a contactindication value indicative of a state of contact between the distal endportion of the medical instrument and the target region based on acriterion combining the impedance magnitude based on the firstelectrical measurement, a ratio of the impedance magnitudes based on thefirst and second electrical measurements, and the phase based on thesecond electrical measurement. The electrical measurements may comprisevoltage, current, and/or other electrical parameter measurements fromwhich impedance measurements (such as impedance magnitude or phase) maybe calculated or may comprise directly-obtained impedance measurements.The criterion may comprise a weighted combination of the impedancemagnitude based on the first electrical measurement, a ratio of theimpedance magnitudes based on the first and second electricalmeasurements, and the phase based on the second electrical measurementor the criterion may comprise an if-then case conditional criterion.

In some embodiments, the system further comprises the medicalinstrument, which may be a radiofrequency ablation catheter. The firstfrequency and the second frequency may be different. In someembodiments, the second frequency is higher than the first frequency. Inother embodiments, the second frequency is lower than the firstfrequency. In some embodiments, the first frequency and the secondfrequency are between 5 kHz and 1000 kHz (e.g., between 5 kHz and 50kHz, between 10 kHz and 100 kHz, between 50 kHz and 200 kHz, between 100kHz and 500 kHz, between 200 kHz and 800 kHz, between 400 kHz and 1000kHz, or overlapping ranges thereof). In various embodiments, the twofrequencies are at least 20 kHz apart in frequency.

In some embodiments, the processor is further configured to generateoutput corresponding to the contact indication value for display on adisplay monitor, upon execution of specific instructions stored in or ona computer-readable medium. In some embodiments, the output comprises anumerical value between 0 and 1. In some embodiments, the outputcomprises a qualitative output (such as a color and/or patternindicative of the contact state). In some embodiments, the outputcomprises one or more of a gauge, a bar, a meter or a scale. In oneembodiment, the output comprises a virtual gauge having a plurality ofregions (e.g., two, three, four, five or more than five regions orsegments) indicative of varying levels of contact, or contact states.The plurality of regions may be represented in different colors. Each ofthe plurality of regions may correspond to a different range ofnumerical values indicative of varying levels of contact.

In accordance with several embodiments, a system for displaying acontact state of a distal tip of a medical instrument with a targetregion (e.g., body tissue) on a patient monitor comprises a processorconfigured to generate output for display on the patient monitor. Theoutput may be generated on a graphical user interface on the patientmonitor. In one embodiment, the output comprises a graph that displays acontact function indicative of a contact state between a distal tip of amedical instrument and body tissue calculated by a processing devicebased, at least in part, on impedance measurements obtained by themedical instrument. The graph may be a scrolling waveform. The outputalso comprises a gauge separate from the graph that indicates areal-time state of contact corresponding to a real-time numerical valueof the contact function displayed by the graph. The gauge includes aplurality of regions indicative of varying contact states. In someembodiments, each one of the plurality of regions is optionallydisplayed in a different color or graduation to provide a qualitativeindication of the real-time state of contact. In one embodiment, thegauge consists of three regions or segments. The three regions may becolored red, yellow and green. In another embodiment, the gauge consistsof four regions or segments. The four regions may be colored red,orange, yellow and green. Each of the plurality of regions maycorrespond to a different range of numerical values indicative of thecurrent contact state. The gauge may comprise a pointer that indicates alevel on the gauge corresponding to the real-time numerical value of thecontact function. The real-time numerical value may range between 0 and1 or between 0 and 1.25 or between 0 and 1.5. Values above 1 maygenerate a “contact alert” to the clinician to prevent excessivecontact, which could result in perforation of tissue. By way of example,the gauge may comprise a contact indicator of the quality oftissue-electrode contact calculated based on bipolar impedancemagnitude, bipolar impedance-frequency slope and bipolar impedancephase.

The output may also comprise other graphs or waveforms of individualcomponents of impedance measurements (e.g., impedance magnitude andphase) at multiple frequencies or of comparisons (e.g., a slope) betweentwo impedance measurements (e.g., impedance magnitude at two differentfrequencies).

In some embodiments, the contact function is calculated based on aweighted combination of a magnitude of a first impedance measurement ata first frequency, a ratio of the magnitudes of the first impedancemeasurement and a second impedance measurement at a second frequencydifferent from the first frequency, and the phase of the secondimpedance measurement at the second frequency. In one embodiment, thesecond frequency is higher than the first frequency. In anotherembodiment, the second frequency is lower than the first frequency. Thefirst frequency and the second frequency may be between 5 kHz and 1000kHz. In some embodiments, the system further comprises the patientmonitor.

In accordance with several embodiments, a system for assessing a levelof contact between a distal end portion of an ablation catheter having apair of spaced-apart electrode members of a combination electrodeassembly and target region, e.g., tissue, comprises a signal sourceconfigured to generate signals having at least a first frequency and asecond frequency to be applied to the pair of spaced-apart electrodemembers. The system also comprises a processor configured to, uponexecution of specific program instructions stored on a computer-readablestorage medium, measure network parameters at an input of a networkmeasurement circuit comprising a plurality of hardware componentsbetween the signal source and the pair of spaced-apart electrodemembers. The processor may also be configured (e.g., specificallyprogrammed, constructed or designed) to determine an aggregate effect ona measured network parameter value caused by the hardware components ofthe network measurement circuit, remove the aggregate effect to resultin a corrected network parameter value between the pair of spaced-apartelectrode members, and determine a level of contact based, at least inpart, on the corrected network parameter value.

In some embodiments, the processor is configured to generate an outputindicative of the level of contact for display. The signal source may belocated within a radiofrequency generator or within the ablationcatheter. The processor may be configured to measure network parametersat at least two frequencies (e.g., two frequencies, three frequencies,four frequencies or more than four frequencies). In some embodiments,the frequencies are between 5 kHz and 1000 kHz. In embodiments involvingtwo frequencies, the second frequency may be at least 20 kHz higher thanthe first frequency. For example, the first frequency may be between 10kHz and 100 kHz and the second frequency is between 400 kHz and 1000kHz. A third frequency may be higher than the first frequency and lowerthan the second frequency (e.g., the third frequency may be between 20kHz and 120 kHz.).

The network parameters may comprise scattering parameters or otherelectrical parameters (such as voltage, current, impedance). The networkparameter values may comprise, for example, voltage and current valuesor impedance values either directly measured or determined from voltageand/or current values. Impedance values may comprise impedance magnitudevalues and impedance phase values. The impedance magnitude values may beobtained at two or more frequencies and slopes may be determined betweenmagnitude values at different frequencies. The impedance phase valuesmay be obtained at one or more frequencies.

In accordance with several embodiments, a method of assessing a level ofcontact determination of a distal end portion of an ablation catheterhaving a pair of spaced-apart electrode members comprises measuringnetwork parameters at an input of a network parameter circuit ofhardware components between a signal source and the pair of spaced-apartelectrode members. The method also comprises determining an aggregateeffect on a measured network parameter value determined from the networkparameters caused by the hardware components, removing the aggregateeffect to result in a corrected network parameter value between the pairof spaced-apart electrode members, and determining a level of contactbased, at least in part, on the corrected network parameter value.

Measuring network parameters may comprise measuring network parametersat a plurality of frequencies. In some embodiments, determining anaggregate effect on the measured network parameter value caused by thehardware components of the network parameter circuit comprises measuringnetwork parameters associated with each individual hardware component.In some embodiments, determining an aggregate effect on the measurednetwork parameter value caused by the hardware components of the networkparameter circuit comprises combining the network parameters of theindividual hardware components into total network parameters at aplurality of frequencies. Removing the aggregate effect so as to isolatean actual network parameter value between the pair of spaced-apartelectrode members may comprise de-embedding the total network parametersfrom a measured input reflection coefficient to result in an actualreflection coefficient corresponding to the actual network parametervalue. In some embodiments, the method is performed automatically by aprocessor. The method may further comprise applying a signal adapted tocause ablative energy to be delivered by the pair of spaced-apartelectrode members sufficient to ablate or otherwise treat cardiac orother body tissue.

In accordance with several embodiments, a system comprises a signalsource (for example, a source of radiofrequency energy or excitationsignals) configured to deliver signals having at least a first frequencyand a second frequency to a pair of electrode members of a combinationelectrode assembly (for example, spaced-apart bipolar pair of electrodemembers) positioned along a distal end portion of a medical instrument(for example, radiofrequency ablation catheter). The embodiment of thesystem also comprises a processing device (for example, specific-purposeprocessor) configured to, upon execution of specific programinstructions stored on a computer-readable storage medium: cause thesignal source to generate and apply the signals to the pair of electrodemembers, obtain electrical measurements (for example, bipolar contactimpedance measurements that are directly measured or that are calculatedor otherwise determined from voltage and/or current measurements)between the pair of electrode members while signals having at least thefirst frequency and the second frequency are being applied to the pairof electrode members, process the electrical measurements obtained atthe first frequency and the second frequency, and determine whether thecombination electrode assembly is in contact with tissue based on saidprocessing of the electrical measurements. The processing device isconfigured to generate an output indicative of contact. The output maycomprise any type of output described herein (for example, visual,audible) and may be output on a display in communication with theprocessing device. The embodiment of the system may comprise a contactsensing subsystem including the signal source and the processing device.The system may also comprise an ablative energy source configured togenerate and apply power to the combination electrode assembly forablating the target region, as described herein. The processing devicemay be configured (for example, specifically programmed) to adjust oneor more energy delivery parameters of the ablative energy based on adetermination of whether the combination electrode assembly is incontact with tissue and/or to terminate energy delivery based on adetermination of whether the combination electrode assembly is incontact with tissue. In some embodiments, the ablative energy source andthe signal source comprise a single source. In some embodiments, thesignal source comprises a first source and the ablative energy sourcecomprises a second source that is separate and distinct from the firstsource. In some embodiments, the contact sensing subsystem is locatedwithin the energy delivery device. In some embodiments where the signalsource and the ablative energy source are separate sources, the contactsensing subsystem is located within a housing that also houses theablative energy source.

The embodiment of the system optionally comprises the medical instrumentitself. The medical instrument may consist essentially of or comprise anablation catheter comprising an elongate body having a proximal end anda distal end and wherein the energy delivery device comprises thecombination electrode assembly. The combination electrode assemblyincludes a first electrode member positioned along the elongate body(for example, at a distal terminus) and a second electrode memberpositioned adjacent the first electrode member (for example, spacedapart by a gap sufficient to electrically insulate the two electrodemembers). The two electrode members may be positioned, shaped, sizedand/or designed (for example, configured) to contact tissue of asubject. The combination electrode assembly also includes anelectrically insulating gap positioned between the first electrodemember and the second electrode member, the electrically insulating gapcomprising a gap width separating the first and second electrodemembers.

In some embodiments, the processing device of the system is configuredto determine an impedance magnitude value based on a first electricalmeasurement obtained from the signal at the first frequency and todetermine an impedance magnitude value and an impedance phase anglevalue based on a second electrical measurement obtained from the signalat the second frequency. In some embodiments, the processing device isconfigured to calculate a contact indication value indicative of a stateof contact between the distal end portion of the medical instrument andthe target region based on a criterion combining the impedance magnitudevalue based on the first electrical measurement, a ratio of theimpedance magnitude values based on the first electrical measurement andthe second electrical measurement, and the impedance phase based on thesecond electrical measurement. The criterion may comprise a weightedcombination of the impedance magnitude based on the first electricalmeasurement, a ratio of the impedance magnitude values based on thefirst and second electrical measurements, and the impedance phase valuebased on the second electrical measurement or the criterion may comprisean if-then conditional criterion. In some embodiments, the signalsgenerated and applied to the pair of electrode members do not travel toa patch electrode remote from the target region so as to facilitatebipolar contact measurements between the two electrode members.

As described herein, the processing device of the embodiment of thesystem may be configured to measure network parameters at an input of anetwork measurement circuit comprising a plurality of hardwarecomponents between the signal source and the pair of electrode members,determine an aggregate effect on a measured network parameter valuecaused by the hardware components of the network measurement circuit,remove the aggregate effect to result in a corrected network parametervalue between the pair of electrode members, and determine a level ofcontact between the pair of electrode members and tissue based, at leastin part, on the corrected network parameter value. The first appliedfrequency may be between 10 kHz and 100 kHz and the second appliedfrequency may be between 400 kHz and 1000 kHz. In some embodiments, thesignal source is further configured to generate a signal having a thirdfrequency to be applied to the pair of spaced-apart electrode membersand the processing device is further configured to measure networkparameters at the third frequency. In some embodiments, the thirdfrequency is higher than the first frequency and lower than the secondfrequency. In various embodiments, the third frequency is between 20 kHzand 120 kHz. The network parameters may be scattering parameters orimpedance parameters. The network parameter values may be impedancevalues comprised of bipolar impedance magnitude values, bipolarimpedance phase values and/or bipolar slope values between impedancemagnitude values at different frequencies.

In accordance with several embodiments, a kit comprises a radiofrequencygenerator comprising an ablative energy source, an ablation cathetercomprising a pair of electrode members separated by a gap positionedalong a distal end portion of the ablation catheter; and a contactsensing subsystem comprising a signal source configured to generate andapply signals having at least two different frequencies to the pair ofelectrode members and a processor configured to determine a level ofcontact between the pair of electrode members and target tissue based,at least in part, on electrical measurements between the pair ofelectrode members while the signals having the at least two differentfrequencies are being applied.

The contact sensing subsystem of the kit may be housed within theradiofrequency generator or may be a separate component from theradiofrequency generator. The kit may optionally comprise electricalcables for connecting the ablation catheter to the radiofrequencygenerator and/or for connecting the ablation catheter to the contactsensing subsystem. The radiofrequency generator may include anintegrated display and the contact sensing subsystem may be configuredto generate an output indicative of the level of contact to the display.

According to some embodiments, an ablation system consists essentiallyof a catheter, an ablation member (e.g., a RF electrode, a composite(e.g., split-tip) electrode, another type of high-resolution electrode,etc.), an irrigation conduit extending through an interior of thecatheter to or near the ablation member, at least one electricalconductor (e.g., wire, cable, etc.) to selectively activate the ablationmember and at least one heat transfer member that places at least aportion of the ablation member (e.g., a proximal portion of the ablationmember) in thermal communication with the irrigation conduit, at leastone heat shunt member configured to effectively transfer heat away fromthe electrode and/or tissue being treated and a plurality of temperaturesensors (e.g., thermocouples) located along two different longitudinallocations of the catheter, wherein the temperature sensors are thermallyisolated from the electrode and configured to detect temperature oftissue at a depth.

In accordance with several embodiments, a system for compensating fordrift in electrode-tissue contact impedance values over time caused bychanges in blood impedance comprises or consists essentially of a signalsource configured to deliver signals to a first set of electrodespositioned along a distal end portion of a medical instrument (e.g., RFablation catheter) that is configured to be positioned in contact withtarget body tissue (e.g., cardiac tissue) and at least one processingdevice. The at least one processing device is communicatively coupled tothe signal source.

In some embodiments, the at least one processing device is configuredto, upon execution of specific program instructions stored on anon-transitory computer-readable storage medium: determine referenceimpedance values (e.g., bipolar impedance values) while signals havingthe least one frequency (e.g., a single frequency or two frequencies)are applied to a second set of electrodes not in contact with the targetbody tissue, adjust contact impedance values (e.g., bipolar impedancevalues) obtained while signals having the at least one frequency areapplied to the first set of electrodes based on the reference impedancevalues, and calculate contact indication values indicative of a level ofcontact (e.g., no contact, poor contact, medium contact, good contact)between the distal end portion of the medical instrument and the targetbody tissue using the adjusted contact impedance values.

In some embodiments, the signal source is configured to deliver signalshaving at least a first frequency to a first set of electrode memberspositioned along a distal end portion of a medical instrument that isconfigured to be positioned in contact with target body tissue and to asecond set of electrodes that is not likely to be in contact with targetbody tissue and the at least one processing device is configured to,upon execution of specific program instructions stored on anon-transitory computer-readable storage medium: cause the signal sourceto generate and apply the signals to the second set of electrodes,determine at least one reference impedance value between the second setof electrodes while signals having at least the first frequency arebeing applied to the second set of electrodes, cause the signal sourceto generate and apply the signals to the first set of electrodes,determine at least one contact impedance value between the first set ofelectrodes, adjust the at least one contact impedance value based on theat least one reference impedance value and calculate a contactindication value indicative of a level of contact between the distal endportion of the medical instrument and the target body tissue using theat least one adjusted actual impedance value.

The first set of electrodes may comprise a bipolar pair of electrodes.The bipolar pair of electrodes may be a proximal and distal electrodemember of a combination electrode assembly configured for bothhigh-resolution mapping and tissue ablation. The second set ofelectrodes may comprise a pair of reference electrodes (or three, fouror more electrodes) positioned along the medical instrument at alocation proximal to the first set of electrodes. For example, the pairof electrodes may comprise a pair of spaced-apart ring electrodes thatare used for mapping in addition to being used for referencemeasurements to correct for drift. In some embodiments, the second setof electrodes comprises a pair of reference electrodes or othermeasurement devices on a separate device from the medical instrument.The signals delivered by the signal source may have at least onefrequency (e.g., one frequency, two different frequencies, threedifferent frequencies) configured to facilitate electrical measurements(e.g., direct impedance measurements or impedance values obtained fromvoltage and/or current measurements) that are in turn used to facilitateelectrode-tissue contact assessment (e.g., whether in contact or not ora qualitative assessment of contact state or level).

In some embodiments, the reference impedance values (e.g., bipolarimpedance values) are calculated from one or more electricalmeasurements (e.g., at least one voltage measurement and at least onecurrent measurement) obtained using the pair of electrodes not incontact with the target body tissue. In some embodiments, the second setof electrodes is the same set of electrodes as the first set ofelectrodes but reference measurements or values are obtained at a timewhen the first set of electrodes are not in contact with the target bodytissue. In some embodiments involving a pair of spaced-apart ringelectrodes as the second set of electrodes, a distal one of the ringelectrodes is separated from a proximal one of the first set ofelectrodes by a distance between 2 mm and 5 mm and a distance between aproximal edge of the distal one of the ring electrodes and a distal edgeof a proximal one of the ring electrodes is between 1 mm and 3 mm.

In some embodiments, the reference impedance values comprise a firstreference bipolar impedance value for an impedance magnitude at thefirst frequency, a second reference bipolar impedance value for a slopebetween the impedance magnitude at the first frequency and an impedancemagnitude at a second frequency, and a third reference bipolar impedancevalue for a phase at the second frequency. In such embodiments, the atleast one processing device may be configured to adjust the firstbipolar contact impedance value based on the first reference bipolarimpedance value, adjust the second bipolar contact impedance value basedon the second reference bipolar impedance value, and adjust the thirdbipolar contact impedance value based on the third reference bipolarimpedance value. The at least one processing device may also beconfigured to calculate the contact indication values using the adjustedfirst, second and third bipolar contact impedance values.

In some embodiments, the first set of electrodes comprises a pair ofelectrode members of a combination electrode assembly. The combinationelectrode assembly may comprise a first electrode member positionedalong an elongate body and a second electrode member positioned adjacentthe first electrode member, with the first electrode member and thesecond electrode member being configured to contact tissue of a subject.An electrically insulating gap is positioned between the first electrodemember and the second electrode member, the electrically insulating gapcomprising a gap width separating the first and second electrodemembers. A filtering element (e.g., a capacitor) may be positionedwithin the gap width.

The signal source may comprises a source of radiofrequency energyconfigured to generate signals having a single frequency or signals atmultiple different frequencies (e.g., a first frequency and a secondfrequency). The first and second frequencies may be between 5 kHz and1000 kHz. In some embodiments, the second frequency is greater than thefirst frequency.

In some embodiments, the system for correcting, or accounting for, driftcomprises an ablative energy source configured to generate and applypower to the first set of electrodes (e.g., a combination electrodeassembly) for ablating the target body tissue. The at least oneprocessing device may be further configured to generate an outputindicative of a level of contact based on the calculated contactindication value and to cause the output to be displayed on a display incommunication with the at least one processing device. The ablativeenergy source and the signal source may consist of a single source ormay be separate and distinct sources. In some embodiments, the systemcomprises a contact sensing subsystem that includes (e.g., resideswithin or is communicatively coupled to) the signal source, and/or theat least one processing device. In some embodiments, the contact sensingsubsystem is housed within a housing of a radiofrequency energygenerator.

In accordance with several embodiments, a method of compensating for(e.g., correcting for or accounting for) drift in electrode-tissuecontact impedance values over time caused by changes in blood impedance(e.g., due to introduction of liquids during an ablation procedure)comprises or consists essentially of determining reference impedancevalues based on electrical measurements obtained using a pair ofelectrode members positioned along a medical instrument when theelectrode members are in contact with blood, determining bipolar contactimpedance values using the pair of electrode members when the electrodemembers are positioned in contact with target tissue at a target tissueablation site, and adjusting the bipolar contact impedance values basedon the determined reference impedance values, thereby resulting inadjusted bipolar contact impedance values that compensate for drift inthe bipolar contact impedance values caused by changes in bloodimpedance over time. The method may further comprise determining thatthe one or more measurement devices are not in contact with tissue. Insome embodiments, the step of adjusting the contact impedance valuescomprises determining proportionality (or other relationship) betweenthe determined reference impedance values or the drift in the determinedreference impedance values and the bipolar contact impedance values orthe drift in the bipolar contact impedance values, and applying acorrection factor, or scaling value, based on the determinedproportionality (or other relationship).

In accordance with several embodiments, a method of compensating fordrift in electrode-tissue contact impedance values over time caused bychanges in blood impedance comprises or consists essentially ofdetermining reference impedance values (e.g., bipolar impedance values)based on electrical measurements obtained using one or more measurementdevices in contact with blood, determining contact impedance values(e.g., bipolar impedance values) using a pair of electrode memberspositioned at a distal end portion of a medical instrument in contactwith target tissue at the target tissue ablation site, and adjusting thecontact impedance values based on the determined reference impedancevalues, thereby resulting in adjusted contact impedance values thatcompensate for drift in the contact impedance values caused by changesin blood impedance and/or resistivity over time. The step of determiningreference impedance values may comprise determining that the pair ofelectrode members is not in contact with tissue. In some embodiments,the step of adjusting the contact impedance values comprises determiningproportionality or other relationship between the determined referenceimpedance values and the contact impedance values and applying acorrection factor based on the determined proportionality or otherrelationship.

In accordance with several embodiments, a method of compensating fordrift in electrode-tissue contact impedance values over time caused bychanges in blood impedance comprises or consists essentially ofdetermining reference impedance values based on electrical measurementsobtained using one or more measurement devices in contact with blood butnot in contact with tissue, determining contact impedance values (e.g.,bipolar impedance values) using a pair of electrode members of acombination electrode assembly positioned at a distal end portion of amedical instrument in contact with target tissue at the target tissueablation site, and adjusting the contact impedance values based on thedetermined reference impedance values, thereby resulting in adjustedcontact impedance values that compensate for drift in the contactimpedance values caused by changes in blood impedance and/or resistivityover time. The electrical measurements comprise at least one voltagemeasurement and at least one current measurement. The step ofdetermining reference impedance values based on electrical measurementsobtained using one or more measurement devices in contact with bloodadjacent to a target tissue ablation site but not in contact with tissuemay comprise positioning the pair of electrode members of thecombination electrode assembly at a location so as not to be in contactwith tissue and determining reference impedance values based onelectrical measurements obtained using the pair of electrode members ofthe combination electrode assembly. In some implementations, the one ormore measurement devices comprise two spaced-apart ring electrodespositioned along the medical instrument at a location proximal to thepair of electrode members of the combination electrode assembly. Themethod may further comprise calculating contact indication valuesindicative of a qualitative assessment of contact using the adjustedcontact impedance values.

In accordance with several embodiments, a method of compensating fordrift in electrode-tissue contact impedance values (e.g., bipolarimpedance values) over time caused by changes in blood impedancecomprises or consists essentially of determining reference impedancevalues (e.g., bipolar impedance values) using a pair of referenceelectrodes at a time when the pair of reference electrodes is in contactwith blood but not in contact with tissue, determining contact impedancevalues (e.g., bipolar impedance values) using a pair of electrodemembers of a combination electrode assembly positioned at a distal endportion of a medical instrument in contact with target tissue at atarget tissue ablation site, and adjusting the contact impedance valuesbased on the determined reference impedance values, thereby resulting inadjusted contact impedance values that compensate for drift in thecontact impedance values caused by changes in blood resistivity orimpedance over time.

In some embodiments, the step of determining reference impedance valuescomprises calculating reference impedance values (e.g., bipolarimpedance values) from one or more electrical measurements (e.g., atleast one voltage measurement and at least one current measurement)obtained using the pair of reference electrodes. The pair of referenceelectrodes may comprise two spaced-apart ring electrodes positionedalong the medical instrument at a location proximal to the pair ofelectrode members of the combination electrode assembly. A distal one ofthe ring electrodes may be separated from a proximal one of the pair ofelectrode members of the combination electrode assembly by a distancebetween 2 mm and 5 mm. A distance between a proximal edge of the distalone of the ring electrodes and a distal edge of a proximal one of thering electrodes may be between 1 mm and 3 mm.

In some embodiments, the step of determining reference impedance valuescomprises determining a first reference bipolar impedance value for animpedance magnitude while a signal having a first frequency is beingapplied to the pair of reference electrodes, determining a secondreference bipolar impedance value for a slope between the impedancemagnitude while the signal having the first frequency is being appliedto the pair of reference electrodes and an impedance magnitude while asignal having a second frequency is being applied to the pair ofreference electrodes, and determining a third reference bipolarimpedance value for a phase while the signal having the second frequencyis being applied to the pair of reference electrodes. In someembodiments, the step of determining bipolar contact impedance valuescomprises determining a first bipolar contact impedance value for animpedance magnitude while the signal having the first frequency is beingapplied to the combination electrode assembly, determining a secondbipolar contact impedance value for a slope between the impedancemagnitude while the signal having the first frequency is being appliedto the combination electrode assembly and an impedance magnitude whilethe signal having the second frequency is being applied to thecombination electrode assembly, and determining a third bipolar contactimpedance value for a phase while the signal having the second frequencyis being applied to the combination electrode assembly. In someembodiments, the step of adjusting the bipolar contact impedance valuescomprises adjusting the first bipolar contact impedance value based onthe first reference bipolar impedance value, adjusting the secondbipolar contact impedance value based on the second reference bipolarimpedance value, and adjusting the third bipolar contact impedance valuebased on the third reference bipolar impedance value. The method mayfurther comprise calculating a contact indication value using theadjusted first, second and third bipolar contact impedance values orcalculating contact indication values indicative of a qualitativeassessment of contact using the adjusted bipolar contact impedancevalues.

Any of the methods or portions thereof described in the Summary sectionabove or in the Detailed Description below may be performed by one ormore processing devices even if only a single processor is described.Any of the drift correction methods described herein may beautomatically performed by at least one processing device of a contactsensing subsystem of an energy delivery system. The processing device(s)(e.g., processor or controller) may be configured to perform operationsrecited herein upon execution of instructions stored within memory or anon-transitory storage medium. The terms “processor,” “processingdevice” and “controller” may be replaced with the plural forms of thewords and should not be limited to a single device but could includemultiple processors, processing devices or controllers in communicationwith each other (e.g., operating in parallel). The methods summarizedabove and set forth in further detail below may describe certain actionstaken by a practitioner; however, it should be understood that they canalso include the instruction of those actions by another party. Forexample, actions such as “terminating energy delivery” include“instructing the terminating of energy delivery.” Further aspects ofembodiments of the invention will be discussed in the following portionsof the specification. With respect to the drawings, elements from onefigure may be combined with elements from the other figures.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentapplication are described with reference to drawings of certainembodiments, which are intended to illustrate, but not to limit, theconcepts disclosed herein. The attached drawings are provided for thepurpose of illustrating concepts of at least some of the embodimentsdisclosed herein and may not be to scale.

FIG. 1 schematically illustrates one embodiment of an energy deliverysystem configured to selectively ablate or otherwise heat targetedtissue of a subject;

FIG. 2 illustrates a side view of a system's catheter comprising ahigh-resolution-tip design according to one embodiment;

FIG. 3 illustrates a side view of a system's catheter comprising ahigh-resolution-tip design according to another embodiment;

FIG. 4 illustrates a side view of a system's catheter comprising ahigh-resolution-tip design according to yet another embodiment;

FIG. 5 illustrates an embodiment of a system's catheter comprising twohigh-resolution-section electrodes each consisting of separate sectionscircumferentially distributed on the catheter shaft;

FIG. 6 schematically illustrates one embodiment of a high-pass filteringelement consisting of a coupling capacitor. The filtering element can beincorporated into a system's catheter that comprises ahigh-resolution-tip design;

FIG. 7 schematically illustrates one embodiment of four high-passfiltering elements comprising coupling capacitors. The filteringelements can operatively couple, in the operating RF frequency range,the separate electrode sections of a system's catheter electrodes, e.g.,those illustrated in FIG. 5;

FIG. 8 illustrates embodiments of EKGs obtained from ahigh-resolution-tip electrode systems disclosed herein configured todetect whether an ablation procedure has been adequately performed;

FIG. 9 illustrates a perspective view of an ablation system's cathetercomprising an electrode and heat shunt network to facilitate thetransfer of heat to an irrigation conduit during use, according to oneembodiment;

FIG. 10 illustrates a partially exposed view of the system of FIG. 9;

FIG. 11 illustrates a perspective view of an ablation system's cathetercomprising an electrode and heat shunt network to facilitate thetransfer of heat to an irrigation conduit during use, according toanother embodiment;

FIG. 12 illustrates a cross-sectional view of an ablation system'scatheter comprising an electrode and heat shunt network to facilitatethe transfer of heat to an irrigation conduit during use, according toone embodiment;

FIG. 13 illustrates a partial cross-sectional perspective view of oneembodiment of an ablation system's catheter comprising an openirrigation cooling system;

FIG. 14 illustrates a partial cross-sectional perspective view of oneembodiment of an ablation system's catheter comprising a closedirrigation cooling system;

FIG. 15 illustrates a partial cross-sectional perspective view ofanother embodiment of an ablation system's catheter;

FIG. 16A illustrates a side perspective view of a distal end of oneembodiment of a composite (e.g., split-tip) RF ablation systemcomprising heat transfer (e.g. heat shunt) members;

FIG. 16B illustrates a partial cross-sectional perspective view of thesystem of FIG. 16A;

FIG. 16C illustrates a partial cross-sectional perspective view ofanother embodiment of an ablation system comprising a compositeelectrode and heat transfer (e.g. heat shunt) members;

FIG. 17A illustrates a side perspective view of a distal end of oneembodiment of a composite (e.g., split-tip) RF ablation systemcomprising heat transfer (e.g. heat shunt) members and fluid outletsextending through a proximal electrode or slug;

FIG. 17B illustrates a partial cross-sectional perspective view of thesystem of FIG. 17A;

FIG. 18A illustrates a perspective view of a distal portion of anopen-irrigated ablation catheter having multiple temperature-measurementdevices, according to one embodiment;

FIGS. 18B and 18C illustrate a perspective view and a cross-sectionalview, respectively, of a distal portion of an open-irrigated ablationcatheter having multiple temperature-measurement devices, according toanother embodiment;

FIG. 18D illustrates a perspective view of a distal portion of anablation catheter having multiple temperature-measurement devices,according to another embodiment;

FIGS. 18E and 18F illustrate a perspective view and a cross-sectionalview, respectively, of a distal portion of an ablation catheter showingisolation of the distal temperature-measurement devices from anelectrode tip, according to one embodiment;

FIG. 19A illustrates a perspective view of a distal portion of aclosed-irrigation ablation catheter having multipletemperature-measurement devices, according to one embodiment;

FIGS. 19B and 19C illustrate a perspective view and a cross-sectionalview, respectively, of a distal portion of a closed-irrigation ablationcatheter having multiple temperature-measurement devices, according toanother embodiment;

FIG. 19D illustrates a perspective view of a distal portion of anopen-irrigated ablation catheter comprising a non-split-tip or othernon-composite design according to one embodiment;

FIG. 20 illustrates a cross-sectional perspective view of one embodimentof a catheter comprising a layer or coating along an exterior of heatshunting members or portions;

FIG. 21A schematically illustrates a distal portion of an open-irrigatedablation catheter in contact with tissue to be ablated in aperpendicular orientation and a lesion formed using the ablationcatheter, according to one embodiment;

FIG. 21B schematically illustrates a distal portion of an open-irrigatedablation catheter in contact with tissue to be ablated in a parallelorientation and a lesion formed using the ablation catheter, accordingto one embodiment;

FIG. 22A is a graph illustrating that temperature of a lesion peak maybe correlated to the temperature of the temperature-measurement devicesby a correction factor or function, according to one embodiment;

FIG. 22B is a plot showing an estimated peak temperature determined byan embodiment of an ablation catheter having multipletemperature-measurement devices compared against actual tissuemeasurements at various depths within a tissue;

FIGS. 23A and 23B illustrate plots showing temperature measurementsobtained by the multiple temperature-measurement devices of anembodiment of an ablation catheter for a parallel orientation and anoblique orientation, respectively;

FIG. 23C illustrates an embodiment of a process for determiningorientation of a distal end of an ablation catheter based, at least inpart, on temperature measurements obtained by the multipletemperature-measurement devices of an embodiment of the ablationcatheter;

FIGS. 23D and 23E illustrate embodiments of flow processes fordetermining orientation of a distal end of an ablation catheter;

FIGS. 23F-1, 23F-2 and 23F-3 illustrate example embodiments of outputindicative of a determined orientation;

FIG. 24 schematically illustrates one embodiment of variable frequencybeing applied to the high-resolution tip, or composite, electrode designof FIG. 2 to determine whether the tip electrode is in contact withtissue;

FIG. 25A is a plot showing normalized resistance of blood/saline andtissue across a range of frequencies;

FIG. 25B is a plot of a four tone waveform utilized for impedancemeasurements;

FIG. 25C is a plot of impedance vs. frequency, with tones at fourfrequencies;

FIG. 25D schematically illustrates one embodiment of a contact sensingsubsystem configured to perform contact sensing functions whilesimultaneously conducting electrogram (EGM) measurements, in accordancewith one embodiment;

FIG. 26A illustrates zero crossings of a frequency spectrum and is usedto illustrate that switching between frequencies may be designed tooccur at the zero crossings to avoid interference at EGM frequencies;

FIG. 26B schematically illustrates one embodiment of a circuit model todescribe the behavior of the impedance of tissue or blood orblood/saline combination, as measured across two electrodes or electrodeportions;

FIG. 26C schematically illustrates one embodiment of a circuitconfigured to switch between contact sensing circuitry in standby modeand radiofrequency energy delivery circuitry in treatment mode, inaccordance with one embodiment;

FIG. 27 schematically illustrates one embodiment of a circuit configuredto perform contact sensing functions while radiofrequency energy isbeing delivered, in accordance with one embodiment;

FIG. 28 is a plot of impedance of an LC circuit element across a rangeof frequencies;

FIG. 29 is a plot showing resistance, or impedance magnitude, values ofablated tissue, viable tissue and blood across a range of frequencies;

FIG. 30 is a plot showing the phase of impedance values of ablatedtissue, viable tissue and blood across a range of frequencies;

FIG. 31 illustrates one embodiment of a sensing algorithm that utilizesimpedance magnitude, ratio of impedance magnitude at two frequencies,and impedance phase data to determine contact state as well as tissuestate;

FIG. 32 illustrates an embodiment of a contact criterion process, andFIG. 32A illustrates an embodiment of a sub-process of the contactcriterion process of FIG. 32;

FIG. 33 illustrates an embodiment of a graphical user interface of adisplay of output indicative of tissue contact by a high resolutioncombination electrode device;

FIG. 34A illustrates a schematic representation of possible hardwarecomponents of a network measurement circuit;

FIG. 34B illustrates a schematic representation of an embodiment of anauto-calibration circuit configured to calibrate (e.g., automatically)the network measurement circuit so as to remove the effects of one ormore hardware components present in the circuit;

FIG. 34C illustrates a schematic representation of one embodiment of anequivalent circuit model for a hardware component present in animpedance measurement circuit;

FIG. 35 illustrates embodiments of EKGs obtained from ahigh-resolution-tip electrode systems disclosed herein configured todetect whether an ablation procedure has been adequately performed;

FIGS. 36A and 36B illustrate different embodiments of a graphicalrepresentation of a target anatomical area being ablated together withablation data and/or information;

FIG. 37A illustrates one embodiment of a graphical representation thatis configured to provide data and/or information regarding specificablations along targeted portions of a subject's anatomy;

FIG. 37B illustrates another embodiment of a graphical representationthat is configured to provide data and/or information regarding specificablations along targeted portions of a subject's anatomy;

FIGS. 38 and 39 illustrates another embodiment of a graphicalrepresentation that is configured to provide data and/or informationregarding specific ablations along targeted portions of a subject'sanatomy;

FIGS. 40A and 40B illustrate different embodiments of 3D tissue mapsthat have been enhanced by high-resolution data obtained;

FIG. 41A illustrates an embodiment of an ablation catheter in which afirst set of electrodes at a distal tip of the ablation catheter is incontact with tissue and a second set of electrodes spaced proximal ofthe first set of electrodes is not in contact with tissue; and

FIG. 41B schematically illustrates an embodiment of a circuit connectionbetween the electrode members of the ablation catheter of FIG. 41A and acontact sensing subsystem or module of an energy delivery system.

DETAILED DESCRIPTION

According to some embodiments, successful electrophysiology proceduresrequire precise knowledge about the anatomic substrate being targeted.Additionally, it may be desirable to evaluate the outcome of an ablationprocedure within a short period of time after the execution of theprocedure (e.g., to confirm that the desired clinical outcome wasachieved). Typically, ablation catheters include only regular mappingelectrodes (e.g., ECG electrodes). However, in some embodiments, it maybe desirable for such catheters to incorporate high-resolution mappingcapabilities. In some embodiments, high-resolution mapping electrodescan provide more accurate and more detailed information about theanatomic substrate and about the outcome of ablation procedures. Forexample, such high-resolution mapping electrodes can allow theelectrophysiology (EP) practitioner to evaluate the morphology ofelectrograms, their amplitude and width and/or to determine changes inpacing thresholds. According to some arrangements, morphology, amplitudeand/or pacing threshold are accepted as reliable EP markers that provideuseful information about the outcome of ablation. Thus, high-resolutionelectrodes are defined as any electrode(s) capable of deliveringablative or other energy to tissue capable of transferring heat to/fromsuch tissue, while being capable of obtaining accurate mapping data ofadjacent tissue, and include, without limitation, composite (e.g.,split-tip) RF electrodes, other closely oriented electrodes or electrodeportions and/or the like.

According to some embodiments, the present application disclosesdevices, systems and/or methods that include one or more of thefollowing features: a high-resolution electrode (e.g., split tipelectrode), heat shunting concepts to help dissipate heat away from theelectrode and/or the tissue of the subject being treated, multipletemperature sensors located along the exterior of the device todetermine, among other things, temperature of the subject at a depth andcontact sensing features that help determine if and to what extent thedevice is contacting targeted tissue.

Several embodiments of the invention are particularly advantageousbecause they include one, several or all of the following benefits: (i)provides the ability to obtain accurate tissue mapping data using thesame electrode that delivers the ablative energy, (ii) reduces proximaledge heating, (iii) reduces likelihood of char or thrombus formation,(iv) provides feedback that may be used to adjust ablation procedures inreal time, (v) provides noninvasive temperature measurements, (vi) doesnot require use of radiometry; (vii) provides tissue temperaturemonitoring and feedback during irrigated or non-irrigated ablation;(viii) provides multiple forms of output or feedback to a user; (ix)provides safer and more reliable ablation procedures, (x) confirmationof actual tissue contact that is easily ascertainable; (xi) confirmationof contact with ablated vs. unablated (viable) tissue that is easilyascertainable; (xii) low cost, as the invention does not require anyspecialized sensor; and/or does not require use of remote patchelectrode(s) for tissue contact sensing or detection; and/or (xiii) morereliable contact indication or assessment.

High-Resolution Electrode

According to some embodiments, various implementations of electrodes(e.g., radiofrequency or RF electrodes) that can be used forhigh-resolution mapping are disclosed herein. For example, as discussedin greater detail herein, an ablation or other energy delivery systemcan comprise a high-resolution-tip design, wherein the energy deliverymember (e.g., radiofrequency electrode) comprises two or more separateelectrodes or electrode portions. As also discussed herein, in someembodiments, such separate electrodes or electrode portions can beadvantageously electrically coupled to each other (e.g., to collectivelycreate the desired heating or ablation of targeted tissue).

FIG. 1 schematically illustrates one embodiment of a treatment (e.g.,energy delivery) system 10 that is configured to selectively ablate,stimulate, modulate and/or otherwise heat or treat targeted tissue(e.g., cardiac tissue, pulmonary vein, other vessels or organs, etc.).Although certain embodiments disclosed herein are described withreference to ablation systems and methods, any of the systems andmethods can be used to stimulate, modulate, heat and/or otherwise affecttissue, with or without partial or complete ablation, as desired orrequired. As shown, the system 10 can include a medical instrument 20(e.g., catheter) comprising one or more energy delivery members 30(e.g., radiofrequency electrodes) along a distal end of the medicalinstrument 20. The medical instrument can be sized, shaped and/orotherwise configured to be passed intraluminally (e.g., intravascularly)through a subject being treated. In various embodiments, the medicalinstrument 20 comprises a catheter, a shaft, a wire, and/or otherelongate instrument. In other embodiments, the medical instrument is notpositioned intravascularly but is positioned extravascularly vialaparoscopic or open surgical procedures. In various embodiments, themedical instrument 20 comprises a catheter, a shaft, a wire, and/orother elongate instrument. In some embodiments, one or more temperaturesensing devices or systems 60 (e.g., thermocouples, thermistors,radiometers, etc.) may be included at the distal end of the medicalinstrument 20, or along its elongate shaft or in its handle. The term“distal end” does not necessarily mean the distal terminus or distalend. Distal end could mean the distal terminus or a location spaced fromthe distal terminus but generally at a distal end portion of the medicalinstrument 20. The medical instrument 20 may optionally include mappingelectrodes (e.g., proximal ring electrodes).

In some embodiments, the medical instrument 20 is operatively coupled toone or more devices or components. For example, as depicted in FIG. 1,the medical instrument 20 can be coupled to a delivery module 40 (suchas an energy delivery module). According to some arrangements, theenergy delivery module 40 includes an energy generation device 42 thatis configured to selectively energize and/or otherwise activate theenergy delivery member(s) 30 (e.g., radiofrequency electrodes) locatedalong the medical instrument 20. In some embodiments, for instance, theenergy generation device 42 comprises one or more signal sources, suchas a radiofrequency generator, an ultrasound energy source, a microwaveenergy source, a laser/light source, another type of energy source orgenerator, and the like, and combinations thereof. In other embodiments,energy generation device 42 is substituted with or used in addition to asource of fluid, such as a cryogenic fluid or other fluid that modulatestemperature. Likewise, the delivery module (e.g., delivery module 40),as used herein, can also be a cryogenic device or other device that isconfigured for thermal modulation.

With continued reference to the schematic of FIG. 1, the energy deliverymodule 40 can include one or more input/output devices or components 44,such as, for example, a touchscreen device, a screen or other display, acontroller (e.g., button, knob, switch, dial, etc.), keypad, mouse,joystick, trackpad, or other input device and/or the like. Such devicescan permit a physician or other user to enter information into and/orreceive information from the system 10. In some embodiments, the outputdevice 44 can include a touchscreen or other display that providestissue temperature information, contact information, other measurementinformation and/or other data or indicators that can be useful forregulating a particular treatment procedure (for example, on one or moregraphical user interfaces generated by the processor 46). Theinput/output devices or components 44 may include an electrophysiologymonitor and/or mapping or navigation systems. In some embodiments, theinput devices or components are integrated into the output devices orcomponents. For example, a touchscreen input interface or input keypadsor knobs or switches may be integrated into a display monitor or theenergy delivery module 40 (for example, generator or control unit).

According to some embodiments, the energy delivery module 40 includes aprocessor 46 (e.g., a processing or control device) that is configuredto regulate one or more aspects of the treatment system 10. The deliverymodule 40 can also comprise a memory unit or other storage device 48(e.g., non-transitory computer readable medium) that can be used tostore operational parameters and/or other data related to the operationof the system 10. In some embodiments, the processor 46 comprises or isin communication with a contact sensing and/or a tissue type detectionmodule or subsystem. The contact sensing subsystem or module may beadapted to determine whether or not the energy delivery member(s) 30 ofthe medical instrument 20 are in contact with tissue (for example,contact sufficient to provide effective energy delivery). In someembodiments, the processor 46 is configured to determine whether thetissue in contact with the one or more energy delivery member(s) 30 hasbeen ablated or otherwise treated. In some embodiments, the system 10comprises a contact sensing subsystem 50. The contact sensing subsystem50 may be communicatively coupled to the processor 46 and/or comprises aseparate controller or processor and memory or other storage media. Thecontact sensing subsystem 50 may perform both contact sensing and tissuetype determination functions. The contact sensing subsystem 50 may be adiscrete, standalone sub-component of the system (as shown schematicallyin FIG. 1) or may be integrated into the energy delivery module 40 orthe medical instrument 20. Additional details regarding a contactsensing subsystem are provided below. The tissue type detection moduleor subsystem may be adapted to determine whether tissue is viable orablated. In some embodiments, the processor 46 is configured toautomatically regulate the delivery of energy from the energy generationdevice 42 to the energy delivery member 30 of the medical instrument 20based on one or more operational schemes. For example, energy providedto the energy delivery member 30 (and thus, the amount of heattransferred to or from the targeted tissue) can be regulated based on,among other things, the detected temperature of the tissue beingtreated, whether the tissue is determined to have been ablated, orwhether the energy delivery member 30 is determined to be in contact“sufficient” contact, or contact above a threshold level) with thetissue to be treated.

According to some embodiments, the energy delivery system 10 can includeone or more temperature detection devices, such as, for example,reference temperature devices (e.g., thermocouples, thermistors,radiometers, etc.) and/or the like. For example, in some embodiments,the device further comprises a one or more temperature sensors or othertemperature-measuring devices to help determine (e.g., detect) a peak(e.g., high or peak, low or trough, etc.) temperature of tissue beingtreated (e.g., at a depth (e.g., relative to a tissue surface)), todetect orientation of a treatment or monitoring portion of a medicalinstrument (for example, a distal end portion of a catheter comprising ahigh-resolution electrode assembly). In some embodiments, thetemperature sensors (e.g., thermocouples) located at, along and/or nearthe ablation member (e.g., RF electrode) can help with the determinationof whether contact is being made between the ablation member andtargeted tissue (and/or to what degree such contact is being made). Insome embodiments, such peak temperature is determined without the use ofradiometry. Additional details regarding the use of temperature sensors(e.g., thermocouples) to determine peak tissue temperature and/or toconfirm or evaluate tissue contact are provided herein.

With reference to FIG. 1, the energy delivery system 10 comprises (or isin configured to be placed in fluid communication with) an irrigationfluid system 70. In some embodiments, as schematically illustrated inFIG. 1, such a fluid system 70 is at least partially separate from theenergy delivery module 40 and/or other components of the system 10.However, in other embodiments, the irrigation fluid system 70 isincorporated, at least partially, into the energy delivery module 40.The irrigation fluid system 70 can include one or more pumps or otherfluid transfer devices that are configured to selectively move fluid(e.g., biocompatible fluid such as saline) through one or more lumens orother passages of the catheter 20. Such fluid can be used to selectivelycool (e.g., transfer heat away from) the energy delivery member 30during use. In other embodiments, the system 10 does not comprise anirrigation fluid system 70.

FIG. 2 illustrates one embodiment of a distal end of a medicalinstrument (e.g., catheter or other elongate member) 20. As shown, themedical instrument (e.g., catheter) 20 can include a high-resolution,combination electrode (e.g., split tip) design, such that there are twoadjacent electrodes or two adjacent electrode members or portions 30A,30B separated by a gap G. According to some embodiments, as depicted inthe configuration of FIG. 2, the relative length of the differentelectrodes or electrode portions 30A, 30B can vary. For example, thelength of the proximal electrode 30B can be between 1 to 20 times (e.g.,1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13,13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20, values between theforegoing ranges, etc.) the length of the distal electrode 30A, asdesired or required. In other embodiments, the length of the proximalelectrode 30B can be greater than 20 times (e.g., 20-25, 25-30, morethan 30 times, etc.) the length of the distal electrode 30A. In yetother embodiments, the lengths of the distal and proximal electrodes30A, 30B are about equal. In some embodiments, the distal electrode 30Ais longer than the proximal electrode 30B (e.g., by 1 to 20 times, suchas, for example, 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11,11-12, 12-13, 13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20, valuesbetween the foregoing ranges, etc.).

In some embodiments, the distal electrode or electrode portion 30A is0.5 mm-0.9 mm long. In some embodiments, the distal electrode orelectrode portion 30A is between 0.1 mm and 1.51 mm long (e.g., 0.1-1.0,0.1-0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 07.0.-0.8,0.8-0.9, 0.9-1.0, 1.0-1.1, 1.1-1.2, 1.2-1.3, 1.3-1.4, 1.4-1.51 mm,values between the foregoing ranges, etc.). In other embodiments, thedistal electrode or electrode portion 30A is greater than 1 mm or 1.51mm in length, as desired or required. In some embodiments, the proximalelectrode or electrode portion 30B is 2 to 4 mm long (e.g., 2-2.5,2.5-3, 3-3.5, 3.5-4 mm, lengths between the foregoing, etc.). However,in other embodiments, the proximal electrode portion 30B is greater than4 mm (e.g., 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 mm, greater than 10 mm, etc.)or smaller than 1 mm (e.g., 0.1-0.5 0.5-1, 1-1.5, 1.5-2 mm, lengthsbetween the foregoing ranges, etc.), as desired or required. Inembodiments where the high-resolution electrodes or portions are locatedon catheter shafts, the length of the electrodes can be 1 to 5 mm (e.g.,1-2, 2-3, 3-4, 4-5 mm, lengths between the foregoing, etc.). However, inother embodiments, the electrodes or electrode portions can be longerthan 5 mm (e.g., 5-6, 6-7, 7-8, 8-9, 9-10, 10-15, 15-20 mm, lengthsbetween the foregoing, lengths greater than 20 mm, etc.), as desired orrequired.

In accordance with several embodiments, the use of a high-resolution,combination electrode, or composite tip (e.g., split-tip) design canpermit a user to simultaneously ablate or otherwise thermally treattargeted tissue and map (e.g., using high-resolution mapping) in asingle configuration. Thus, such systems can advantageously permitprecise high-resolution mapping (e.g., to confirm that a desired levelof treatment occurred) during a procedure. In some embodiments, thehigh-resolution tip design that includes two electrodes or electrodeportions 30A, 30B can be used to record a high-resolution bipolarelectrogram. For such purposes, the two electrodes or electrode portions30A,30B can be connected to the inputs of an EP recorder. In someembodiments, a relatively small separation distance (e.g., gap G)between the electrodes or electrode portions 30A, 30B enableshigh-resolution mapping.

In some embodiments, a medical instrument (e.g., a catheter) 20 caninclude three or more electrodes or electrode portions (e.g., separatedby gaps), as desired or required. Additional details regarding sucharrangements are provided below. According to some embodiments,regardless of how many electrodes or electrode portions are positionedalong a catheter tip, the electrodes or electrode portions 30A, 30B areradiofrequency electrodes and comprise one or more metals, such as, forexample, stainless steel, platinum, platinum-iridium, gold, gold-platedalloys and/or the like.

According to some embodiments, as illustrated in FIG. 2, the electrodesor electrode portions 30A, 30B are spaced apart from each other (e.g.,longitudinally or axially) using a gap (e.g., an electrically insulatinggap). In some embodiments, the length of the gap G (or the separationdistance between adjacent electrodes or electrode portions) is 0.5 mm.In other embodiments, the gap G or separation distance is greater orsmaller than 0.5 mm, such as, for example, 0.1-1 mm (e.g., 0.1-0.2,0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0mm, values between the foregoing ranges, less than 0.1 mm, greater than1 mm, etc.), as desired or required.

According to some embodiments, a separator 34 is positioned within thegap G, between the adjacent electrodes or electrode portions 30A, 30B,as depicted in FIG. 2. The separator can comprise one or moreelectrically insulating materials, such as, for example, Teflon,polyetheretherketone (PEEK), polyetherimide resins (e.g., ULTEM™),diamond (e.g., industrial grade diamond), ceramic materials, polyimideand the like.

As noted above with respect to the gap G separating the adjacentelectrodes or electrode portion, the insulating separator 34 can be 0.5mm long. In other embodiments, the length of the separator 34 can begreater or smaller than 0.5 mm (e.g., 0.1-0.2, 0.2-0.3, 0.3-0.4,0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0 mm, values betweenthe foregoing ranges, less than 0.1 mm, greater than 1 mm, etc.), asdesired or required.

According to some embodiments, as discussed in greater detail herein, toablate or otherwise heat or treat targeted tissue of a subjectsuccessfully with the high-resolution tip electrode design, such as theone depicted in FIG. 2, the two electrodes or electrode portions 30A,30B are electrically coupled to each other at the RF treatment (e.g.,ablation) frequency or range of RF treatment frequencies. Thus, the twoelectrodes or electrode portions can advantageously function as (e.g.,behave like) a single longer electrode at the RF treatment frequency orrange of treatment frequencies (e.g., frequencies between 400 kHz and600 kHz) whereas the two electrodes or electrode portions behave asseparate electrodes at frequencies used for mapping purposes (e.g.,frequencies less than 1 kHz). For clarity, a filtering element such asdescribed below, may have a value such that at ablative or othertreatment frequencies, the filtering element effectively shorts the twoelectrodes or electrode portions such that the two electrodes orelectrode portions behave as a single composite tip electrode duringablation or treatment and the filtering element effectively presents anopen circuit between the two electrodes or electrode portions such thatthey behave as electrically separated distinct electrodes for mappingpurposes (e.g., EGM mapping or recording). As shown, one of theelectrode portions (for example, the distal electrode) 30A can beelectrically coupled to an energy delivery module 40 (for example, an RFgenerator). As discussed herein, the module 40 can comprise one or morecomponents or features, such as, for example, an energy generationdevice that is configured to selectively energize and/or otherwiseactivate the energy members (for example, RF electrodes), one or moreinput/output devices or components, a processor (for example, aprocessing or control device) that is configured to regulate one or moreaspects of the treatment system, a memory and/or the like.

FIGS. 3 and 4 illustrate different embodiments of catheter systems 100,200 that incorporate a high-resolution tip design. For example, in FIG.3, the electrode (e.g., radiofrequency electrode) along the distal endof the electrode comprises a first or distal electrode or electrodeportion 110 and a second or proximal electrode or electrode portion 114.As shown and discussed in greater detail herein with reference to otherconfigurations, the high-resolution tip design 100 includes a gap Gbetween the first and second electrodes or electrode portions 110, 114.In some configurations, the second or proximal electrode or electrodeportion 114 is generally longer than the first or distal electrode orelectrode portion 110. For instance, the length of the proximalelectrode 114 can be between 1 to 20 times (e.g., 1-2, 2-3, 3-4, 4-5,5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-16,16-17, 17-18, 18-19, 19-20, values between the foregoing ranges, etc.)the length of the distal electrode 110, as desired or required. In otherembodiments, the length of the proximal electrode can be greater than 20times (e.g., 20-25, 25-30, more than 30 times, etc.) the length of thedistal electrode. In yet other embodiments, the lengths of the distaland proximal electrodes are about the same. However, in someembodiments, the distal electrode 110 is longer than the proximalelectrode 114 (e.g., by 1 to 20 times, such as, for example, 1-2, 2-3,3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15,15-16, 16-17, 17-18, 18-19, 19-20, values between the foregoing ranges,etc.).

As shown in FIG. 3 and noted above, regardless of their exact design,relative length diameter, orientation and/or other characteristics, theelectrodes or electrode portions 110, 114 can be separated by a gap G.The gap G can comprise a relatively small electrically insulating gap orspace. In some embodiments, an electrically insulating separator 118 canbe snugly positioned between the first and second electrodes orelectrode portions 110, 114. In certain embodiments, the separator 118can have a length of about 0.5 mm. In other embodiments, however, thelength of the separator 118 can be greater or smaller than 0.5 mm (e.g.,0.1-0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9,0.9-1.0 mm, values between the foregoing ranges, less than 0.1 mm,greater than 1 mm, etc.), as desired or required. The separator caninclude one or more electrically insulating materials (e.g., materialsthat have an electrical conductivity less than about 1000 or less (e.g.,500-600, 600-700, 700-800, 800-900, 900-1000, 1000-1100, 1100-1200,1200-1300, 1300-1400, 1400-1500, values between the foregoing, less than500, greater than 1500, etc.) than the electrical conductivity of metalsor alloys). The separator can comprise one or more electricallyinsulating materials, such as, for example, Teflon, polyetheretherketone(PEEK), polyoxymethylene, acetal resins or polymers and the like.

As shown in FIG. 3, the separator 118 can be cylindrical in shape andcan have the identical or similar diameter and configuration as theadjacent electrodes or electrode portions 110, 114. Thus, in someembodiments, the outer surface formed by the electrodes or electrodeportions 110, 114 and the separator 118 can be generally uniform orsmooth. However, in other embodiments, the shape, size (e.g., diameter)and/or other characteristics of the separator 118 can be different thanone or more of the adjacent electrodes or electrode portions 110, 114,as desired or required for a particular application or use.

FIG. 4 illustrates an embodiment of a system 200 having three or moreelectrodes or electrode portions 210, 212, 214 separated bycorresponding gaps G1, G2. The use of such additional gaps, and thus,additional electrodes or electrode portions 210, 212, 214 that arephysically separated (e.g., by gaps) yet in close proximity to eachother, can provide additional benefits to the high-resolution mappingcapabilities of the system. For example, the use of two (or more) gapscan provide more accurate high-resolution mapping data related to thetissue being treated. Such multiple gaps can provide information aboutthe directionality of cardiac signal propagation. In addition,high-resolution mapping with high-resolution electrode portionsinvolving multiple gaps can provide a more extended view of lesionprogression during the ablation process and higher confidence thatviable tissue strands are not left behind within the targetedtherapeutic volume. In some embodiments, high-resolution electrodes withmultiple gaps can optimize the ratio of mapped tissue surface to ablatedtissue surface. Preferably, such ratio is in the range of 0.2 to 0.8(e.g., 0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, ratiosbetween the foregoing, etc.). Although FIG. 4 illustrates an embodimenthaving a total of three electrodes or electrode portions 210, 212, 214(and thus, two gaps G1, G2), a system can be designed or otherwisemodified to comprise additional electrodes or electrode portions, andthus, additional gaps. For example, in some embodiments, an ablation orother treatment system can include 4 or more (e.g., 5, 6, 7, 8, morethan 8, etc.) electrodes or electrode portions (and thus, 3 or moregaps, e.g., 3, 4, 5, 6, 7 gaps, more than 7 gaps, etc.), as desired orrequired. In such configurations, a gap (and/or an electrical separator218 a, 218 b) can be positioned between adjacent electrodes or electrodeportions, in accordance with the embodiments illustrated in FIGS. 2 to4.

As depicted in FIGS. 3 and 4, an irrigation tube 120, 220 can be routedwithin an interior of the catheter (not shown for clarity). In someembodiments, the irrigation tube 120, 220 can extend from a proximalportion of the catheter (e.g., where it can be placed in fluidcommunication with a fluid pump) to the distal end of the system. Forexample, in some arrangements, as illustrated in the side views of FIGS.3 and 4, the irrigation tube 120, 220 extends and is in fluidcommunication with one or more fluid ports 211 that extend radiallyoutwardly through the distal electrode 110, 210. Thus, in someembodiments, the treatment system comprises an open irrigation design,wherein saline and/or other fluid is selectively delivered through thecatheter (e.g., within the fluid tube 120, 220) and radially outwardlythrough one or more outlet ports 111, 211 of an electrode 110, 210. Thedelivery of such saline or other fluid can help remove heat away fromthe electrodes and/or the tissue being treated. In some embodiments,such an open irrigation system can help prevent overheating of targetedtissue, especially along the tissue that is contacted by the electrodes.An open irrigation design is also incorporated in the system that isschematically illustrated in FIG. 2. For instance, as depicted in FIG.2, the distal electrode or electrode portion 34 can include a pluralityof outlet ports 36 through which saline or other irrigation fluid canexit.

According to some embodiments, a catheter can include ahigh-resolution-tip electrode design that includes one or more gaps inthe circumferential direction (e.g., radially), either in addition to orin lieu of gaps in the longitudinal direction. One embodiment of asystem 300 comprising one or more electrodes 310A, 310B is illustratedin FIG. 5. As shown, in arrangements where two or more electrodes areincluded, the electrodes 310A, 310B can be longitudinally or axiallyoffset from each other. For example, in some embodiments, the electrodes310A, 310B are located along or near the distal end of a catheter. Insome embodiments, the electrodes 310A, 310B are located along anexterior portion of a catheter or other medical instrument. However, inother configurations, one or more of the electrodes can be positionedalong a different portion of the catheter or other medical instrument(e.g., along at least an interior portion of a catheter), as desired orrequired.

With continued reference to FIG. 5, each electrode 310A, 310B cancomprises two or more sections 320A, 322A and/or 320B, 322B. As shown,in some embodiments, the each section 320A, 322A and/or 320B, 322B canextend half-way around (e.g., 180 degrees) the diameter of the catheter.However, in other embodiments, the circumferential extent of eachsection can be less than 180 degrees. For example, each section canextend between 0 and 180 degrees (e.g., 15, 30, 45, 60, 75, 90, 105, 120degrees, degrees between the foregoing, etc.) around the circumferenceof the catheter along which it is mounted. Thus, in some embodiments, anelectrode can include 2, 3, 4, 5, 6 or more circumferential sections, asdesired or required.

Regardless of how the circumferential electrode sections are designedand oriented, electrically insulating gaps G can be provided betweenadjacent sections to facilitate the ability to use the electrode toconduct high-resolution mapping, in accordance with the variousembodiments disclosed herein. Further, as illustrated in the embodimentof FIG. 5, two or more (e.g., 3, 4, 5, more than 5, etc.) electrodes310A, 310B having two or more circumferential or radial sections can beincluded in a particular system 300, as desired or required.

In alternative embodiments, the various embodiments of a high-resolutiontip design disclosed herein, or variations thereof, can be used with anon-irrigated system or a closed-irrigation system (e.g., one in whichsaline and/or other fluid is circulated through or within one or moreelectrodes to selectively remove heat therefrom). Thus, in somearrangements, a catheter can include two or more irrigation tubes orconduits. For example, one tube or other conduit can be used to deliverfluid toward or near the electrodes, while a second tube or otherconduit can be used to return the fluid in the reverse direction throughthe catheter.

According to some embodiments, a high-resolution tip electrode isdesigned to balance the current load between the various electrodes orelectrode portions. For example, if a treatment system is not carefullyconfigured, the electrical load may be delivered predominantly to one ormore of the electrodes or electrode portions of the high-resolution tipsystem (e.g., the shorter or smaller distal electrode or electrodeportion). This can lead to undesirable uneven heating of the electrode,and thus, uneven heating (e.g., ablation) of the adjacent tissue of thesubject. Thus, in some embodiments, one or more load balancingconfigurations can be used to help ensure that the heating along thevarious electrodes or electrode portions of the system will be generallybalanced. As a result, the high-resolution tip design can advantageouslyfunction more like a longer, single electrode, as opposed to two or moreelectrodes that receive an unequal electrical load (and thus, deliver anunequal amount of heat or level of treatment to the subject's targetedtissue).

One embodiment of a configuration that can be used to balance theelectrical current load delivered to each of the electrodes or electrodeportions in a high-resolution tip design is schematically illustrated inFIG. 6. As shown, one of the electrodes (e.g., the distal electrode) 30Acan be electrically coupled to an energy delivery module 40 (e.g., a RFgenerator). As discussed herein, the module 40 can comprise one or morecomponents or features, such as, for example, an energy generationdevice that is configured to selectively energize and/or otherwiseactivate the energy members (e.g., RF electrodes), one or moreinput/output devices or components, a processor (e.g., a processing orcontrol unit) that is configured to regulate one or more aspects of thetreatment system, a memory and/or the like. Further, such a module canbe configured to be operated manually or automatically, as desired orrequired.

In the embodiment that is schematically depicted in FIG. 6, the distalelectrode 30A is energized using one or more conductors 82 (e.g., wires,cables, etc.). For example, in some arrangements, the exterior of theirrigation tube 38 comprises and/or is otherwise coated with one or moreelectrically conductive materials (e.g., copper, other metal, etc.).Thus, as shown in FIG. 6, the one or more conductors 82 can be placed incontact with such a conductive surface or portion of the irrigation tube38 to electrically couple the electrode or electrode portion 30A to anenergy delivery module (e.g., energy delivery module 40 of FIG. 1).However, one or more other devices and/or methods of placing theelectrode or electrode portion 30A in electrical communication with anenergy delivery module can be used. For example, one or more wires,cables and/or other conductors can directly or indirectly couple to theelectrodes, without the use of the irrigation tube.

With continued reference to FIG. 6, the first or distal electrode orelectrode portion 30A can be electrically coupled to the second orproximal electrode or electrode portion 30B using one more band-passfiltering elements 84, such as a capacitor, a filter circuit (see, e.g.,FIG. 16), etc. For instance, in some embodiments, the band-passfiltering element 84 comprises a capacitor that electrically couples thetwo electrodes or electrode portions 30A, 30B when radiofrequencycurrent is applied to the system (e.g., radiofrequency current or powerhaving a frequency adapted for ablation or other treatment of tissue).In one embodiment, the capacitor 84 comprises a 100 nF capacitor thatintroduces a series impedance lower than about 3Ω at 500 kHz, which,according to some arrangements, is a target frequency for RF ablation.However, in other embodiments, the capacitance of the capacitor(s) orother band-pass filtering elements 84 that are incorporated into thesystem can be greater or less than 100 nF, for example, 5 nF to 300 nF,according to the operating RF frequency, as desired or required. In someembodiments, the capacitance of the filtering element 84 is selectedbased on a target impedance at a particular frequency or frequencyrange. For example, in some embodiments, the system can be operated at afrequency of 200 kHz to 10 MHz (e.g., 200-300, 300-400, 400-500,500-600, 400-600, 600-700, 700-800, 800-900, 900-1000 kHz, up to 10 MHzor higher frequencies between the foregoing ranges, etc.). Thus, thecapacitor that couples adjacent electrodes or electrode portions to eachother can be selected based on the target impedance for a particularfrequency. For example, a 100 nF capacitor provides about 3Ω of couplingimpedance at an operating ablation frequency of 500 kHz.

In some embodiments, a series impedance of 3Ω across the electrodes orelectrode portions 30A, 30B is sufficiently low when compared to theimpedance of the conductor 82 (e.g., wire, cable, etc.), which can beabout 5-10Ω, and the impedance of tissue, which can be about 100Ω, suchthat the resulting tissue heating profile is not negatively impactedwhen the system is in use. Thus, in some embodiments, a filteringelement is selected so that the series impedance across the electrodesor electrode portions is lower than the impedance of the conductor thatsupplies RF energy to the electrodes. For example, in some embodiments,the insertion impedance of the filtering element is 50% of the conductor82 impedance, or lower, or 10% of the equivalent tissue impedance, orlower.

In some embodiments, a filtering element (e.g., capacitor a filtercircuit such as the one described herein with reference to FIG. 16,etc.) can be located at a variety of locations of the device oraccompanying system. For example, in some embodiments, the filteringelement is located on or within a catheter (e.g., near the distal end ofthe catheter, adjacent the electrode, etc.). In other embodiments,however, the filtering element is separate of the catheter. Forinstance, the filtering element can be positioned within or along ahandle to which the catheter is secured, within the generator or otherenergy delivery module, within a separate processor or other computingdevice or component and/or the like).

Similarly, with reference to the schematic of FIG. 7, a filteringelement 384 can be included in an electrode 310 comprisingcircumferentially-arranged portions 320, 322. In FIG. 7, the filteringelement 384 permits the entire electrode 310 to be energized within RFfrequency range (e.g., when the electrode is activated to ablate). Oneor more RF wires or other conductors 344 can be used to deliver power tothe electrode from a generator or source. In addition, separateconductors 340 can be used to electrically couple the electrode 310 formapping purposes.

In embodiments where the high-resolution-tip design (e.g., FIG. 4)comprises three or more electrodes or electrode portions, additionalfiltering elements (e.g., capacitors) can be used to electrically couplethe electrodes or electrode portions to each other. Such capacitors orother filtering elements can be selected to create a generally uniformheating profile along the entire length of the high-resolution tipelectrode. As noted in greater detail herein, for any of the embodimentsdisclosed herein or variations thereof, the filtering element caninclude something other than a capacitor. For example, in somearrangements, the filtering element comprises a LC circuit (e.g., aresonant circuit, a tank circuit, a tuned circuit, etc.). Suchembodiments can be configured to permit simultaneous application of RFenergy and measurement of EGM recordings.

As discussed above, the relatively small gap G between the adjacentelectrodes or electrode portions 30A, 30B can be used to facilitatehigh-resolution mapping of the targeted tissue. For example, withcontinued reference to the schematic of FIG. 6, the separate electrodesor electrode portions 30A, 30B can be used to generate an electrogramthat accurately reflects the localized electrical potential of thetissue being treated. Thus, a physician or other practitioner using thetreatment system can more accurately detect the impact of the energydelivery to the targeted tissue before, during and/or after a procedure.For example, the more accurate electrogram data that result from suchconfigurations can enable the physician to detect any gaps or portionsof the targeted anatomical region that was not properly ablated orotherwise treated. Specifically, the use of a high-resolution tip designcan enable a cardiac electrophysiologist to more accurately evaluate themorphology of resulting electrograms, their amplitude and width and/orto determine pacing thresholds. In some embodiments, morphology,amplitude and pacing threshold are accepted and reliable EP markers thatprovide useful information about the outcome of an ablation or otherheat treatment procedure.

According to some arrangements, the high-resolution-tip electrodeembodiments disclosed herein are configured to provide localizedhigh-resolution electrogram. For example, the electrogram that isobtained using a high-resolution-tip electrode, in accordance withembodiments disclosed herein, can provide electrogram data (e.g.,graphical output) 400 a, 400 b as illustrated in FIG. 8. As depicted inFIG. 8, the localized electrograms 400 a, 400 b generated using thehigh-resolution-tip electrode embodiments disclosed herein include anamplitude A1, A2.

With continued reference to FIG. 8, the amplitude of the electrograms400 a, 400 b obtained using high-resolution-tip electrode systems can beused to determine whether targeted tissue adjacent thehigh-resolution-tip electrode has been adequately ablated or otherwisetreated. For example, according to some embodiments, the amplitude A1 ofan electrogram 400 a in untreated tissue (e.g., tissue that has not beenablated or otherwise heated) is greater that the amplitude A2 of anelectrogram 400 b that has already been ablated or otherwise treated. Insome embodiments, therefore, the amplitude of the electrogram can bemeasured to determine whether tissue has been treated. For example, theelectrogram amplitude A1 of untreated tissue in a subject can berecorded and used as a baseline. Future electrogram amplitudemeasurements can be obtained and compared against such a baselineamplitude in an effort to determine whether tissue has been ablated orotherwise treated to an adequate or desired degree.

In some embodiments, a comparison is made between such a baselineamplitude (A1) relative to an electrogram amplitude (A2) at a tissuelocation being tested or evaluated. A ratio of A1 to A2 can be used toprovide a quantitative measure for assessing the likelihood thatablation has been completed. In some arrangements, if the ratio (i.e.,A1/A2) is above a certain minimum threshold, then the user can beinformed that the tissue where the A2 amplitude was obtained has beenproperly ablated. For example, in some embodiments, adequate ablation ortreatment can be confirmed when the A1/A2 ratio is greater than 1.5(e.g., 1.5-1.6, 1.6-1.7, 1.7-1.8, 1.8-1.9, 1.9-2.0, 2.0-2.5, 2.5-3.0,values between the foregoing, greater than 3, etc.). However, in otherembodiments, confirmation of ablation can be obtained when the ratio ofA1/A2 is less than 1.5 (e.g., 1-1.1, 1.1-1.2, 1.2-1.3, 1.3-1.4, 1.4-1.5,values between the foregoing, etc.).

For any of the embodiments disclosed herein, a catheter or otherminimally-invasive medical instrument can be delivered to the targetanatomical location of a subject (e.g., atrium, pulmonary veins, othercardiac location, renal artery, other vessel or lumen, etc.) using oneor more imaging technologies. Accordingly, any of the ablation systemsdisclosed herein can be configured to be used with (e.g., separatelyfrom or at least partially integrated with) an imaging device or system,such as, for example, fluoroscopy technologies, intracardiacechocardiography (ICE) technologies and/or the like.

Thermal Shunting

FIG. 9 illustrates one embodiment of a system 1100 comprising anelectrode 1130 (e.g., a unitary RF electrode, a composite (e.g.,split-tip) electrode having two, three or more portions, other types ofelectrodes, etc.) located at or near the distal end of a catheter 1120.In addition, as with any other embodiments disclosed herein, the systemcan further include a plurality of ring electrodes 1170 to assist withthe execution of a treatment procedure (e.g., mapping of tissue adjacentthe treatment site, monitoring of the subject, etc.). Although theembodiments of the various systems and related methods disclosed hereinare described in the context of radiofrequency (RF) based ablation, theheat transfer concepts (including heat shunting embodiments), eitheralone or in conjunction with other embodiments described herein (e.g.,composite electrode concepts, temperature sensing concepts, etc.), canbe implemented in other types of ablation systems as well, such asthose, for example, that use microwave emitters, ultrasound transducers,cryoablation members and/or the like to target tissue of a subject.

With reference to FIG. 9 and the corresponding partially-exposed view ofthe distal end of the catheter illustrated in FIG. 10, one or more heattransfer members or other heat transfer components or features,including any of the heat shunting embodiments disclosed herein, can beused to facilitate the heat transfer from or near the electrode to theirrigation conduit 1108 that extends through the interior of thecatheter 1120. For example, in some embodiments, as depicted in FIG. 10,one or more heat transfer disks or members 1140, 1142 (e.g., heat shuntdisks or members) can be positioned along the length of the electrode1130. In some arrangements, the disks or other heat transfer members1140, 1142 (including any of the heat shunting embodiments disclosedherein) comprise separate components that may or may not contact eachother. In other embodiments, however, the heat transfer disks or otherheat transfer members 1140, 1142 comprise a unitary or monolithicstructure, as desired or required. The disks 1140, 1142 can be in director indirect thermal communication with the irrigation conduit 1108 thatpasses, at least partially, through an interior portion (e.g., along thelongitudinal centerline) of the catheter. For example, the disks 1140,1142 can extend to and make contact with an exterior surface of theirrigation conduit and/or another interior portion of the catheter(e.g., non-irrigation component or portion for embodiments that do notinclude active cooling using open or closed irrigation). However, inother embodiments, as illustrated in FIG. 11, the disks 1140, 1142 canbe in thermal communication (e.g., directly via contact or indirectly)with one or more other heat exchange components or members, includingany heat shunting components or members, located between the disks andthe irrigation conduit.

A heat sink includes both (i) a heat retention transfer in which heat islocalized to/retained by a certain component, and (ii) a heat shunt(which can also be called a heat transfer member) that is used to shuntor transfer heat from, e.g., an electrode to an irrigation passageway.In one embodiment, a heat retention sink is used to retain heat for someperiod of time. Preferably, a heat shunt (heat transfer member) is usedrather than a heat retention sink. A heat shunt (heat transfer member),in some embodiments, provides more efficient dissipation of heat andimproved cooling, thus, for example, offering a protective effect totissue that is considered non-target tissue. For any of the embodimentsdisclosed herein, one or more heat shunting components can be used toeffectively and safely transfer heat away from an electrode and/or thetissue being heated. In some embodiments, a device or system can beconfigured to adequately transfer heat away from the electrode withoutany additional components or features (e.g., solely using the heatshunting configurations disclosed herein).

In any of the embodiments disclosed herein, the ablation system caninclude one or more irrigation conduits that extend at least partiallyalong (e.g., through an interior portion of) a catheter or other medicalinstrument configured for placement within a subject. The irrigationconduit(s) can be part of an open irrigation system, in which fluidexits through one or more exit ports or openings along the distal end ofthe catheter (e.g., at or near the electrode) to cool the electrodeand/or the adjacent targeted tissue. Alternatively, however, theirrigation conduit(s) can be part of a closed irrigation system, inwhich irrigation fluid is circulated at least partially through (e.g.,as opposed to being expelled from) the catheter (e.g., in the vicinityof the electrode or other ablation member to selectively cool theelectrode and/or the adjacent tissue of the subject. For example, insome arrangements, the catheter comprises at least two internal fluidconduits (e.g., a delivery conduit and a return conduit) to circulateirrigation fluid to and perform the desired or necessary heat transferwith the distal end of the catheter, as desired or required. Further, insome embodiments, in order to facilitate the heat transfer between theheat transfer members or components included in the ablation system(e.g., heat shunting members or components), the system can comprise anirrigation conduit that comprises one or more metallic and/or otherfavorable heat transfer materials (e.g., copper, stainless steel, othermetals or alloys, ceramics, polymeric and/or other materials withrelatively favorable heat transfer properties, etc.). In yet otherembodiments, the catheter or other medical instrument of the ablationsystem does not include any active fluid cooling system (e.g., open orclosed irrigation passage or other components extending through it), asdesired or required. As discussed in greater detail herein, suchembodiments that do not include active cooling using fluid passagethrough the catheter can take advantage of enhanced heat transfercomponents and/or designs to advantageously dissipate and/or distributeheat away from the electrode(s) and/or the tissue being treated.

In some embodiments, the irrigation conduit is fluid communication onlywith exit ports located along the distal end of the elongate body. Insome embodiments, the catheter only comprises irrigation exit openingsalong a distal end of the catheter (e.g., along a distal end or theelectrode). In some embodiments, the system does not comprise anyirrigation openings along the heat transfer members (e.g., heat shuntmembers), and/or, as discussed herein, the system does not comprise anactive irrigation system at all. Thus, in such embodiments, the use ofheat transfer members along the catheter (e.g., at or near the electrodeor other ablation member) help more evenly distribute the heat generatedby the electrode or other ablation member and/or assist in heat transferwith the surrounding environment (e.g., blood or other fluid passingalong an exterior of the ablation member and/or catheter).

With continued reference to FIG. 10, the proximal end 1132 of theelectrode 1130 comprises one or more additional heat transfer members1150, including any heat shunt embodiments disclosed herein. Forexample, according to some embodiments, such additional heat transfermembers 1150 (e.g., heat shunt members) comprise one or more fins, pinsand/or other members that are in thermal communication with theirrigation conduit 108 extending through an interior of the catheter ofthe system. Accordingly, as with the heat transfer disks or other heattransfer members 1140 positioned along the length of the electrode 1130,including heat shunting members, heat can be transferred and thusremoved, from the electrode, the adjacent portions of the catheterand/or the adjacent tissue of the subject, when the electrode isactivated, via these heat transfer members 1150.

In any of the embodiments disclosed herein or variations thereof, theheat transfer members 1140, 1150 of the system 1100 that are placed inthermal communication with the irrigation conduit 1108 can comprise oneor more materials that include favorable heat transfer properties,including, but not limited to, favorable heat shunting properties. Forexample, in some embodiments, the thermal conductivity of thematerial(s) included in the heat transfer members and/or of the overallheat transfer assembly (e.g., when viewed as a unitary member orstructure) is greater than 300 W/m/° C. (e.g., 300-350, 350-400,400-450, 450-500, 500-600, 600-700 W/m/° C., ranges between theforegoing, greater than 700 W/m/° C., etc. Possible materials withfavorable thermal conductivity properties include, but are not limitedto, copper, brass, beryllium, other metals and/or alloys, aluminalceramics, other ceramics, industrial diamond (e.g., chemical vapordeposit industrial diamond) and/or other metallic and/or non-metallicmaterials.

According to certain embodiments where the heat transfer memberscomprise heat shunting members, the thermal diffusivity of thematerial(s) included in the heat shunt members and/or of the overallheat shunt assembly (e.g., when viewed as a unitary member or structure)is greater than 1.5 cm²/sec (e.g., 1.5-2, 2-2.5, 2.5-3, 3-4, 4-5, 5-6,6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-20 cm²/sec,values between the foregoing ranges, greater than 20 cm²/sec). Thermaldiffusivity measures the ability of a material to conduct thermal energyrelative to its ability to store thermal energy. Thus, even though amaterial can be efficient as transferring heat (e.g., can have arelatively high thermal conductivity), it may not have favorable thermaldiffusivity properties, because of its heat storage properties. Heatshunting, unlike heat transferring, requires the use of materials thatpossess high thermal conductance properties (e.g., to quickly transferheat through a mass or volume) and a low heat capacity (e.g., to notstore heat). Possible materials with favorable thermal diffusivity, andthus favorable heat shunting properties, include, but are not limitedto, industrial diamond (e.g., chemical vapor deposit industrialdiamond), Graphene, silica, other carbon-based materials and/or thelike.

The use of materials with favorable thermal diffusivity properties canhelp ensure that heat can be efficiently transferred away from theelectrode and/or the adjacent tissue during a treatment procedure. Incontrast, materials that have favorable thermal conductivity properties,but not favorable thermal diffusivity properties, such as, e.g., copper,other metals or alloys, thermally conductive polypropylene or otherpolymers, etc., will tend to retain heat. As a result, the use of suchmaterials that store heat may cause the temperature along the electrodeand/or the tissue being treated to be maintained at an undesirablyelevated level (e.g., over 75 degrees C.) especially over the course ofa relatively long ablation procedure, which may result in charring,thrombus formation and/or other heat-related problems.

Industrial diamond (e.g., chemical vapor deposition industrial diamond)and other materials with the requisite thermal diffusivity propertiesfor use in a thermal shunting network, as disclosed in the variousembodiments herein, comprise favorable thermal conductioncharacteristics. Such favorable thermal conduction aspects emanate froma relatively high thermal conductance value (k) and the manner in whichthe heat shunt members of a network are arranged with respect to eachother within the tip and with respect to the tissue. For example, insome embodiments, as RF energy is emitted from the tip and the ohmicheating within the tissue generates heat, the exposed distal most shuntmember (e.g., located 0.5 mm from the distal most end of the tip) canactively extract heat from the lesion site. The thermal energy canadvantageously transfer through the shunting network in a relativelyrapid manner and dissipate through the shunt residing beneath the RFelectrode surface the heat shunt network, through a proximal shuntmember and/or into the ambient surroundings. Heat that is shuntingthrough an interior shunt member can be quickly transferred to anirrigation conduit extending through an interior of the catheter orother medical instrument. In other embodiments, heat generated by anablation procedure can be shunted through both proximal and distal shuntmembers (e.g., shunt members that are exposed to an exterior of thecatheter or other medical instrument, such as shown in many of theembodiments herein).

Further, as noted above, the materials with favorable thermaldiffusivity properties for use in a heat shunt network not only have therequisite thermal conductivity properties but also have sufficiently lowheat capacity values (c). This helps ensure that the thermal energy isdissipated very quickly from the tip to tissue interface as well as thehot spots on the electrode, without heat retention in the heat shuntingnetwork. The thermal conduction constitutes the primary heat dissipationmechanism that ensures quick and efficient cooling of the tissue surfaceand of the RF electrode surface. Conversely a heat transfer (e.g., withrelatively high thermal conductivity characteristics but also relativelyhigh heat capacity characteristics) will store thermal energy. Over thecourse of a long ablation procedure, such stored heat may exceed 75degrees C. Under such circumstances, thrombus and/or char formation canundesirably occur.

The thermal convection aspects of the various embodiments disclosedherein two-fold. First, an irrigation lumen of the catheter can absorbthermal energy which is transferred to it through the shunt network.Such thermal energy can then be flushed out of the distal end of the RFtip via the irrigation ports. In closed irrigation systems, however,such thermal energy can be transferred back to a proximal end of thecatheter where it can be removed. Second, the exposed shunt surfacesalong an exterior of the catheter or other medical instrument canfurther assist with the dissipation of heat from the electrode and/orthe tissue being treated. For example, such heat dissipation can beaccomplished via the inherent convective cooling aspects of the bloodflowing over the surfaces of the electrode.

Accordingly, the use of materials in a heat shunting network withfavorable thermal diffusivity properties, such as industrial diamond(e.g., chemical vapor deposition industrial diamond), can help ensurethat heat is quickly and efficiently transferred away from the electrodeand treated tissue, while maintaining the heat shunting network cool(e.g., due to its low heat capacity properties). This can create a saferablation catheter and related treatment method, as potentially dangerousheat will not be introduced into the procedure via the heat shuntingnetwork itself.

For example, in some embodiments, during the course of an ablationprocedure that attempts to maintain the subject's tissue at a desiredtemperature of about 60 degrees C., the temperature of the electrode isapproximately 60 degrees Celsius. Further, the temperature oftraditional heat transferring members positioned adjacent the electrode(e.g., copper, other metals or alloys, thermally-conductive polymers,etc.) during the procedure is approximately 70 to 75 degrees Celsius. Incontrast, the temperature of the various portions or members of the heatshunting network for systems disclosed herein can be approximately 60 to62 degrees Celsius (e.g., 10% to 30% less than comparable heattransferring systems) for the same desired level of treatment of tissue.

In some embodiments, the heat shunt members disclosed herein draw outheat from the tissue being ablated and shunt it into the irrigationchannel. Similarly, heat is drawn away from the potential hot spots thatform at the edges of RF electrodes and are shunted through the heatshunt network into the irrigation channel. From the irrigation channel,via convective cooling, heat can be advantageously released into theblood stream and dissipated away. In closed irrigation systems, heat canbe removed from the system without expelling irrigation fluid into thesubject.

According to some embodiments, the various heat shunting systemsdisclosed herein rely on heat conduction as the primary coolingmechanism. Therefore, such embodiments do not require a vast majority ofthe heat shunting network to extend to an external surface of thecatheter or other medical instrument (e.g., for direct exposure to bloodflow). In fact, in some embodiments, the entire shunt network can residewithin an interior of the catheter tip (i.e., with no portion of theheat shut network extending to an exterior of the catheter or othermedical instrument). Further, the various embodiments disclosed hereindo not require electrical isolation of the heat shunts from the RFelectrode or from the irrigation channel.

According to some embodiments, the heat transfer disks and/or other heattransfer members 1140, 1150, 1250A included in a particular system,including heat shunting members or components, can continuously and/orintermittently or partially extend to the irrigation conduit 108, asdesired or required for a particular design or configuration. Forinstance, as illustrated in the embodiment of FIG. 10, the proximal heattransfer member 1150 (e.g., heat shunt members) can comprise one or more(e.g., 2, 3, 4, 5, more than 5, etc.) wings or portions 1154, 1254 thatextend radially outwardly from a base or inner member 1152, 1252. Insome embodiments, such wings or radially-extending portion 1154, 1254are equally spaced from each other to more evenly transfer heat towardthe irrigation conduit 1108 with which the heat transfer member 1150,1250A is in thermal communication. Alternatively, however, the heattransfer member 1150, 1250A, including, but not limited to, a heat shuntmember, can include a generally solid or continuous structure betweenthe irrigation conduit 1108 and a radially exterior portion or region ofthe catheter.

According to some embodiments, heat transfer members (e.g., fins) 1150can extend proximally to the proximal end of the electrode(s) includedalong the distal end of a catheter. For example, as illustrated in FIG.10, the heat transfer members 1150 (e.g., heat shunt members) can extendto, near or beyond the proximal end of the electrode 1130. In someembodiments, the heat transfer members 1150 terminate at or near theproximal end 1132 of the electrode 1130. However, in other arrangements,the heat transfer members 1150, including, without limitation, heatshunt members, extend beyond the proximal end 1132 of the electrode1130, and in some embodiments, contact and/or are otherwise in direct orindirect thermal communication with distally-located heat transfermembers (e.g., heat transfer disks or other heat transfer memberslocated along or near the length of the electrode 1130), including heatshunt members, as desired or required. In yet other embodiments,proximal heat transfer members (e.g., heat shunt members) terminateproximally to the proximal end 1132 of the electrode or other ablationmember.

In any of the embodiments disclosed herein, including the systemscomprising the enhanced heat transfer (e.g., heat shunting) propertiesdiscussed in connection with FIGS. 9-12, the system can include one ormore temperature sensors or temperature detection components (e.g.,thermocouples) for the detection of tissue temperature at a depth. Forexample, in the embodiments illustrated in FIGS. 9 and 10, the electrodeand/or other portion of the distal end of the catheter can include oneor more sensors (e.g., thermocouples, thermistors, etc.) and/or thelike. Thus, signals received by sensors and/or othertemperature-measurement components can be advantageously used todetermine or approximate the extent to which the targeted tissue isbeing treated (e.g., heated, cooled, etc.). Temperature measurements canbe used to control an ablation procedure (e.g., module power provided tothe ablation member, terminate an ablation procedure, etc.), inaccordance with a desired or required protocol.

In some embodiments, the device further comprises a one or moretemperature sensors or other temperature-measuring devices to helpdetermine a peak (e.g., high or peak, low or trough, etc.) temperatureof tissue being treated. In some embodiments, the temperature sensors(e.g., thermocouples) located at, along and/or near the ablation member(e.g., RF electrode) can help with the determination of whether contactis being made between the ablation member and targeted tissue (and/or towhat degree such contact is being made). In some embodiments, such peaktemperature is determined without the use of radiometry. Additionaldetails regarding the use of temperature sensors (e.g., thermocouples)to determine peak tissue temperature and/or to confirm or evaluatetissue contact are provided herein.

In some embodiments, for any of the systems disclosed herein (includingbut not limited to those illustrated herein) or variations thereof, oneor more of the heat transfer members, including, but not limited to,heat shunt members, that facilitate the heat transfer to an irrigationconduit of the catheter are in direct contact with the electrode and/orthe irrigation conduit. However, in other embodiments, one or more ofthe heat transfer members (e.g., heat shunt members) do not contact theelectrode and/or the irrigation conduit. Thus, in such embodiments, theheat transfer members are in thermal communication with the electrodeand/or irrigation conduit, but not in physical contact with suchcomponents. For example, in some embodiments, one or more intermediatecomponents, layers, coatings and/or other members are positioned betweena heat transfer member (e.g., a heat shunt member) and the electrode (orother ablation member) and/or the irrigation conduit.

FIG. 11 illustrates another embodiment of an ablation system 1200comprising an electrode (e.g., a RF electrode, a composite (e.g.,split-tip) electrode, etc.) or other ablation member 1230 located alongor near the distal end of a catheter or other elongated member. In someembodiments, an interior portion 1236 of the electrode or other ablationmember (not shown in FIG. 11, for clarity) can include a separate,internal heat transfer member 1250B, including any heat shuntembodiments disclosed herein. Such a heat transfer member 1250B can bein addition to or in lieu of any other heat transfer members located at,within and/or near the electrode or other ablation member. For example,in the depicted embodiment, in the vicinity of the electrode 1230, thesystem 1200 comprises both an internal heat transfer member 1250B andone or more disk-shaped or cylindrical heat transfer members 1240 (e.g.,heat shunting members).

For any of the embodiments disclosed herein, at least a portion of heattransfer member, including a heat shunt member, that is in thermalcommunication with the irrigation conduit extends to an exterior surfaceof the catheter, adjacent to (and, in some embodiments, in physicaland/or thermal contact with) the electrode or other ablation member.Such a configuration, can further enhance the cooling of the electrodeor other ablation member when the system is activated, especially at ornear the proximal end of the electrode or ablation member, where heatmay otherwise tend to be more concentrated (e.g., relative to otherportions of the electrode or other ablation member). According to someembodiments, thermal conductive grease and/or any other thermallyconductive material (e.g., thermally-conductive liquid or other fluid,layer, member, coating and/or portion) can be used to place the thermaltransfer, such as, for example, a heat shunt member or heat shuntnetwork, in thermal communication with the irrigation conduit, asdesired or required. In such embodiments, such a thermally conductivematerial places the electrode in thermal communication, at leastpartially, with the irrigation conduit.

With continued reference to FIG. 11, the heat transfer member (e.g.,heat shunt member) 1250B located along an interior portion of theelectrode 1230 can include one or more fins, wings, pins and/or otherextension members 1254B. Such members 1254B can help enhance heattransfer with the (e.g., heat shunting to, for heat shuntingembodiments) irrigation conduit 1208, can help reduce the overall sizeof the heat transfer member 1254B and/or provide one or more additionaladvantages or benefits to the system 1200.

Another embodiment of an ablation system 1300 comprising one or moreheat transfer (e.g., heat shunt) components or features 1350A, 1350Bthat facilitate the overall heat transfer of the electrode or otherablation member during use is illustrated in FIG. 12. As shown, heattransfer (e.g., shunting) between one or more heat transfer members1350B located along an interior of an electrode or other ablation member1330 can be facilitated and otherwise enhanced by eliminating air gapsor other similar spaces between the electrode and the heat transfermembers. For example, in the illustrated embodiment, one or more layers1356 of an electrically conductive material (e.g., platinum, gold, othermetals or alloys, etc.) have been positioned between the interior of theelectrode 1330 and the exterior of the heat transfer member 1350B. Suchlayer(s) 1356 can be continuously or intermittently applied between theelectrode (or another type of ablation member or energy delivery member)and the adjacent heat transfer member(s), including, but not limited to,heat shunting member(s). Further, such layer(s) 1356 can be appliedusing one or more methods or procedures, such as, for example,sputtering, other plating techniques and/or the like. Such layer(s) 1356can be used in any of the embodiments disclosed herein or variationsthereof.

FIG. 13 illustrates a distal portion of a catheter or other medicalinstrument of an ablation system 1800 comprising one or more heattransfer members 1850 (e.g., heat shunt members) that facilitate theefficient transfer of heat generated by the electrode or other energydelivery member 1830. As shown in FIG. 13, the heat shunt members 1850are positioned immediately adjacent (e.g., within an interior of) theelectrode 1830. Accordingly, as discussed in greater detail herein, heatgenerated by the electrode or other energy delivery member 1830 can betransferred via the one or more heat shunt members 1850. As discussedabove, the heat shunt members advantageously comprise favorable thermaldiffusivity properties to quickly transfer heat while not retainingheat. Thus, the likelihood of localized hot spots (e.g., along thedistal and/or proximal ends of the electrode) can be prevented orreduced. In addition, the heat dissipation or removal (e.g., away fromthe electrode) can be more easily and/or quickly realized using the heatshunt members 1850.

As discussed herein, for example, the heat shunt members 1850 caninclude industrial diamond (e.g., chemical vapor deposition industrialdiamond), Graphene, silica or other carbon-based materials withfavorable thermal diffusivity properties and/or the like. In someembodiments, the heat shunt members 1850 comprise a combination of two,three or more materials and/or portions, components or members. In someembodiments, the thermal diffusivity of the material(s) included in theheat shunt members and/or of the overall heat shunting network orassembly (e.g., when viewed as a unitary member or structure) is greaterthan 1.5 cm²/sec (e.g., 1.5-2, 2-2.5, 2.5-3, 3-4, 4-5, 5-6, 6-7, 7-8,8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-20 cm²/sec, valuesbetween the foregoing ranges, greater than 20 cm²/sec).

The heat shunt members 1850 (e.g., fins, rings, blocks, etc.) can be indirect or indirect contact with the electrode or other energy deliverymember 1830. Regardless of whether direct physical contact is madebetween the electrode and one or more of the heat transfer shunt 1850,the heat shunt members 1850 can be advantageously in thermalcommunication with the electrode, thereby facilitating the heatdissipation and/or heat transfer properties of the catheter or othermedical instrument. In some embodiments, for example, one or moreintermediate layers, coatings, members and/or other components arepositioned between the electrode (or other energy delivery member) andthe heat shunt members, as desired or required.

With continued reference to FIG. 13, as discussed with other embodimentherein, a catheter or other medical instrument of the ablation system1800 comprises an open irrigation system configured to deliver a coolingfluid (e.g., saline) to and through the distal end of the catheter orother medical instrument. Such an open irrigation system can help removeheat from the electrode or other energy delivery member during use. Insome embodiments, the heat shunting network and the favorable thermaldiffusivity properties it possesses can help to quickly and efficientlytransfer heat from the electrode and/or the tissue being treated to anirrigation conduit or passage 1804 or chamber 1820 during use. Forexample, as depicted in FIG. 13, an irrigation conduit or passage 1804extends through an interior of the catheter and is in fluidcommunication with one or more outlet ports 1811 along the distal member1810 of the catheter. However, as discussed in greater detail herein,enhanced heat shunt members can be incorporated into the design of acatheter or other medical instrument without the use of an openirrigation system and/or without an active fluid cooling system, asdesired or required. In some embodiments, the flow of irrigation fluid(e.g., saline) through the irrigation conduit or chamber of the catheteror other medical instrument can be modified to vary the heat shuntingthat occurs through the heat shunting network. For example, in someembodiments, due to the favorable heat transfer properties of the heatshunting network and its ability to not retain heat, the flow rate ofirrigation fluid through a catheter can be maintained below 5 ml/min(e.g., 1-2, 2-3, 3-4, 4-5 ml/min, flow rates between the foregoingranges, less than 1 ml/min, etc.). In one embodiment, the flow rate ofirrigation fluid through a catheter is maintained at approximately 1ml/min. In other embodiments, the flow rate of irrigation fluid passingthrough the catheter can be between 5 and 15 ml/min (e.g., 5-6, 6-7,7-8, 8-9, 9-10, 11-12, 12-13, 13-14, 14-15 ml/min, flow rates betweenthe foregoing rates, etc.) or greater than 15 ml/min (e.g., 15-16,16-17, 17-18, 18-19, 19-20 ml/min, flow rates between the foregoingrates, etc.), as desired or required. In some embodiments, suchirrigation flow rates are significantly less than would otherwise berequired if non-heat shunting members (e.g., metals, alloys,thermally-conductive polymers, other traditional heat transferringmembers, etc.) were being used to transfer heat away from the electrodeand/or the tissue between treated. For example, the required flow rateof the irrigation fluid passing through an interior of a catheter thathas a heat shunting member in accordance with the various embodimentsdisclosed herein or variations thereof, can be decreased by 20% to 90%(e.g., 20-25, 25-30, 30-35, 35-40, 40-45, 45-50, 50-55, 55-60, 60-65,65-70, 70-75, 75-80, 80-85, 85-90%, percentages between the foregoingranges, etc.), as compared to systems that use traditional heattransferring members or no heat transferring members at all (e.g.,assuming the same amount of heating is produced at the electrode, thesame anatomical location is being treated and other parameters are thesame). For example, in some commercially available RF ablation systems,an irrigation flow rate of about 30 ml/min (e.g., 25-35 ml/min) istypically required to accomplish a desired level of heat transfer wayfrom the electrode. As noted above, in some arrangements, the systemsdisclosed herein that utilize a heat shunting network can utilize airrigation flow rate of about 10 ml/min or lower to effectively shuntthe heat away from the electrode. Thus, in such embodiments, theirrigation flow rate can be reduced by at least 60% to 70% relative totraditional and other commercially available systems.

Thus, as noted in greater detail herein, the use of heat shuntingmaterials to shunt heat away from the electrode and/or the adjacenttissue can also reduce the amount of irrigation fluid that is beingdischarged into the subject's blood stream in an open irrigation system.Since the discharge of irrigation fluid into the subject is notdesirable, the use of heat shunting in an ablation catheter can provideadditional benefits to an ablation procedure. For example, in somearrangements, discharging excessive saline or other cooling fluid intothe heart, blood vessel and/or other targeted region of the subject canbring about negative physiological consequences to the subject (e.g.,heart failure).

As noted above, the use of heat shunting components at or near theelectrode can also provide one or more additional benefits andadvantages. For example, a significantly lower irrigation flow rate isrequired to effectively remove heat away from the electrode and thesurrounding tissue using heat shunting components (e.g., vis-à-vistraditional heat transferring components and members), the irrigationfluid in such systems is less likely to negatively impact anytemperature sensors (e.g., sensor 1880 in FIG. 13) that are locatedalong or near the outside of the distal end of a catheter, allowing moreaccurate temperature measurements. This is particularly relevant forsystems, such as those disclosed herein, where temperature sensors areconfigured to detect the temperature of adjacent tissue of a subject(e.g., not the temperature of the electrode or another component orportion of the treatment system). Thus, the lower volume of fluid beingdischarged at or in the vicinity of the sensors (e.g., compared tosystems that do not use heat shunting, systems that include traditionalheat transfer components, systems that rely primarily or strictly onheat transfer between the electrode (and/or tissue) and blood passingadjacent the electrode (and/or tissue), other open-irrigation systems,etc.) can increase the accuracy of the temperature measurements obtainedby the sensors located at or near the distal end of a catheter or othermedical instrument.

Also, since the irrigation fluid can be delivered at a lower flow ratewhich is characterized by a laminar flow profile (e.g., as opposed to aturbulent flow profile that may be required when the irrigation flowrate is higher), any disruptive fluid dynamic effects resulting from anotherwise higher flow rate can be advantageously avoided or at leastreduced. Thus, the laminar flow of fluid (and/or in conjunction with thesignificantly lower flow rate of the fluid relative to higher flowsystems) can help with the accuracy of the temperature measurements bythe sensors located near the electrode, the tissue being treated and/orany other location along the distal end of the catheter or other medicalinstrument.

Further, since heat shunting components positioned along or near theelectrode are so effective in transferring heat away from the electrodeand/or the adjacent tissue of the subject being treated withoutretaining the heat being transferred, the need to have a longerelectrode and/or larger heat transferring members or portions can beadvantageously eliminated. For example, traditional systems that utilizeone or more heat transferring members (as opposed and in contrast toheat shunting members) or systems that do not use any heat transferringmembers or components at all rely on the heat transfer between theelectrode and the surrounding environment (e.g., blood that flows pastthe electrode, irrigation fluid passing through an interior of thecatheter, etc.) to attempt to cool the electrode. As a result, thelength, size and/or other dimensions of the electrode or traditionalheat transferring members needs to be increased. This is done toincrease the surface area for improved heat transfer between theelectrode and/or the heat transferring members and the fluid that willprovide the heat transfer (e.g., blood, irrigation fluid, etc.).However, in various embodiments disclosed herein, it is advantageouslynot necessary to provide such enlarged surface areas for the electrodeand/or the heat shunting components or other members of the heatshunting network. Accordingly, the electrode can be sized based on theintended ablation/heating and/or mapping (e.g., high-resolution)properties without the need to oversize based on heat transfer capacity.Such oversizing can negatively impact the safety and efficacy of alesion formation procedure.

Therefore, as discussed herein, in some embodiments, the size of theheat shunting members can be advantageously reduced (e.g., as comparedto the size of heat transferring members in traditional systems). Heatgenerated during a treatment procedure can be efficiently and rapidlytransferred away from electrode and/or the tissue being treated via theheat shunting network without the fear of such network retaining theheat being transferred. In some embodiments, the heat can be shunted toirrigation fluid passing through an interior of the catheter or othermedical instrument. In other embodiments, heat can be transferred tosurrounding bodily fluid of the subject (e.g., blood) via heat shuntingmembers that are positioned along an exterior of the catheter or othermedical instrument, either in addition or in lieu of heat shunting to anirrigation fluid.

According to some embodiments, the total length (e.g., along alongitudinal direction) of the heat shunting members that extend to theexterior of the catheter or other medical instrument (such as, e.g., inthe configurations depicted in FIGS. 13 to 17B) can be 1 to 3 mm (e.g.,1-1.5, 1.5-2, 2-2.5, 2.5-3 mm, lengths between the foregoing values,etc.). As noted above, despite such a relatively short exposure length,the heat shunting members can effectively transfer heat away from theelectrode and/or the tissue being ablated without retaining heat.

According to some embodiments, the total length (e.g., along alongitudinal direction) of the heat shunting members that extend alongan interior of the catheter or other medical instrument (such as, e.g.,in the configurations depicted in FIGS. 13 to 17B) can be 1 to 30 mm(e.g., 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12,12-13, 13-14, 14-15, 15-20, 20-25, 25-30 mm, lengths between theforegoing values, etc.). As noted above, despite such a relatively shortoverall length, the heat shunting members can effectively transfer heataway from the electrode and/or the tissue being ablated to fluid passingthrough the irrigation channel of the catheter or other medicalinstrument without retaining heat.

According to some embodiments, the total length (e.g., along alongitudinal direction) of the heat shunting members that extend alongan interior of the catheter or other medical instrument plus theelectrode (such as, e.g., in the configurations depicted in FIGS. 13 to17B) can be 1 to 30 mm (e.g., 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9,9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-20, 20-25, 25-30 mm, lengthsbetween the foregoing values, etc.). As noted above, despite such arelatively short overall length, the heat shunting members caneffectively transfer heat away from the electrode and/or the tissuebeing ablated to fluid passing through the irrigation channel of thecatheter or other medical instrument without retaining heat.

As illustrated in FIG. 13, an interior of the distal end of the catheteror other medical instrument can comprise a cooling chamber or region1820 that is in fluid communication with the irrigation conduit orpassage 1804. As shown, according to some embodiments, the coolingchamber 1820 includes a diameter or cross-sectional dimension that isgreater than the diameter or cross-sectional dimension of the fluidconduit or passage 1804. For example, in some arrangements, the diameteror other cross-sectional dimension of the cooling chamber or region 1820is approximately 1 to 3 times (e.g., 1 to 1.1, 1.1 to 1.2, 1.2 to 1.3,1.3 to 1.4, 1.4 to 1.5, 1.5 to 1.6, 1.6 to 1.7, 1.7 to 1.8, 1.8 to 1.9,1.9 to 2.0, 2.0 to 2.1, 2.1 to 2.2, 2.2 to 2.3, 2.3 to 2.4, 2.4 to 2.5,2.5 to 2.6, 2.6 to 2.7, 2.7 to 2.8, 2.8 to 2.9, 2.9 to 3, values betweenthe foregoing, etc.) the diameter or cross-section dimension of thefluid conduit or passage 1804, as desired or required. In otherembodiments, the diameter or other cross-sectional dimension of thecooling chamber or region 1820 is approximately greater than 3 times thediameter or cross-section dimension of the fluid conduit or passage1804, as desired or required (e.g., 3 to 3.5, 3.5 to 4, 4 to 5, valuesbetween the foregoing, greater than 5, etc.). In other embodiments, thediameter or cross-section dimension of the cooling chamber or region1820 is similar or identical to that of the fluid conduit or passage1804 (or smaller than that of the fluid conduit or passage), as desiredor required.

FIG. 14 illustrates a distal end of a catheter or other medicalinstrument of another embodiment of an ablation system 1900. As shown,the catheter comprises one or more energy delivery members 1930 (e.g., asplit-tip composite RF electrode, another type of electrode, anothertype of ablation member, etc.) along its distal end 1910. Like in FIG.13, the depicted arrangement comprises an active cooling system usingone or more fluid conduits or passages that extend at least partiallythrough the interior of the catheter or other medical instrument.

With continued reference to FIG. 14, the catheter or medical instrumentof the ablation system 1900 includes a closed irrigation system (e.g.,non-open irrigation system) in which cooling fluid (e.g., saline) iscirculated at least partially through an interior of the catheter (e.g.,to and/or near the location of the electrode or other energy deliverymember) to transfer heat away from such electrode or other energydelivery member. As shown, the system can include two separate conduitsor passages 1904, 1906 extending at least partially through the interiorof the catheter or other medical instrument configured for placementwithin and/or adjacent targeted tissue of a subject. In someembodiments, one fluid conduit or passage 1904 is configured to deliverfluid (e.g., saline) to the distal end of the catheter or instrument(e.g., adjacent the electrode, ablation member or other energy deliverymember), while a separate conduit or passage 1906 is configured toreturn the cooling fluid delivered to or near the distal end of thecatheter or other medical instrument proximally. In other embodiments,more than one passage or conduit delivers fluid to the distal end and/ormore than one passage or fluid returns fluid from the distal end, asdesired or required.

In the embodiment of FIG. 14, the fluid delivery conduit or passage 1904is in fluid communication with a cooling chamber or region 1920 thatextends within an interior of the electrode or other energy deliverymember 1930. In the depicted arrangement, the outlet 1905 of the fluiddelivery conduit or passage 1904 is located at a location proximal tothe distal end or inlet 1907 of the fluid return conduit or passage1906. Thus, in the illustrated embodiment, the cooling chamber or region1920 generally extends between the outlet 1905 of the fluid deliveryconduit or passage 1904 and the inlet 1907 of the fluid return conduitor passage 1906. However, in other embodiments, the length, orientation,location and/or other details of the cooling chamber or portion 1920 canvary, as desired or required. Further, in some embodiments, a catheteror other medical instrument can include a closed fluid cooling system(e.g., wherein cooling fluid is circulated through the catheter ormedical instrument) without the inclusion of a separate cooling chamberor portion. Regardless of the exact orientation of the various fluiddelivery and/or return lines (e.g., passages, conduits, etc.) of thecatheter or medical instrument in a closed-loop fluid cooling system,fluid is simply circulated through at least a portion of the catheter orother medical instrument (e.g., adjacent and/or in the vicinity of theelectrode or energy delivery member being energized) to selectively andadvantageously transfer heat away from the electrode or energy deliverymember. Thus, in such embodiments, the various fluid conduits orpassages are in thermal communication with the electrode or other energydelivery member.

In some embodiments, it is advantageous to transfer heat away from theelectrode (or other energy delivery member) of an ablation system, andthus, the targeted tissue of the subject, without expelling ordischarging cooling fluid (e.g., saline) into the subject. For example,in some arrangements, discharging saline or other cooling fluid into theheart, blood vessel and/or other targeted region of the subject canbring about negative physiological consequences to the subject (e.g.,heart failure). Thus, in some embodiments, it is preferred to treat asubject with an ablation system that includes a catheter or othermedical instrument with a closed fluid cooling system or without anactive fluid cooling system altogether.

As with the embodiment of FIG. 14 (and/or other embodiments disclosedherein), the depicted catheter includes one or more heat shunt members1950 that are in thermal communication with the electrode, ablationmember or other energy delivery member 1930 of the system 1900. Asdiscussed above, the heat shunt members 1950 can include industrialdiamond, Graphene, silica, other carbon-based materials with favorablethermal diffusivity properties and/or the like. In some embodiments, thethermal diffusivity of the material(s) included in the heat shuntmembers and/or of the overall heat shunt network or assembly (e.g., whenviewed as a unitary member or structure) is greater than 1.5 cm²/sec(e.g., 1.5-2, 2-2.5, 2.5-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11,11-12, 12-13, 13-14, 14-15, 15-20 cm²/sec, values between the foregoingranges, greater than 20 cm²/sec).

FIG. 15 illustrates yet another embodiment of a catheter or othermedical instrument of an ablation system 2000 can includes one or moreheat transfer members 2050 (e.g., heat shunt members) along and/or nearits distal end 2010. Unlike the arrangements of FIGS. 13 and 14discussed herein, the depicted embodiment does not include an activefluid cooling system. In other words, the catheter or other medicalinstrument does not comprise any fluid conduits or passages. Instead, insome embodiments, as illustrated in FIG. 15, the distal end of thecatheter comprises one or more interior members (e.g., interiorstructural members) 2070 along its interior. Such interior members 2070can include a member or material having favorable thermal diffusivitycharacteristics. In some embodiments, the interior member 2070 comprisesidentical or similar thermal diffusivity characteristics or propertiesas the heat shunt members 2050, such as, for example, industrial diamondor Graphene. In some embodiments, the thermal diffusivity of thematerial(s) included in the interior member 2070 and/or of the overallheat shunt network or assembly (e.g., when viewed as a unitary member orstructure) is greater than 1.5 cm²/sec (e.g., 1.5-2, 2-2.5, 2.5-3, 3-4,4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-20cm²/sec, values between the foregoing ranges, greater than 20 cm²/sec).However, in other embodiments, the interior member(s) do not includehigh heat shunting materials and/or members. In other embodiments,however, the interior member 2070 does not include materials or memberssimilar to those as the heat shunt members 2050. For example, in somearrangements, the interior member(s) 2070 can include one or morecomponents or members that comprise material(s) having a thermaldiffusivity less than 1 cm²/sec.

With continued reference to the embodiment of FIG. 15, the volume alongthe distal end of the catheter or medical instrument includes astructural member that at least partially occupies said volume. This isin contrast to other embodiments disclosed herein, wherein at least aportion of the distal end of the catheter or medical instrument includesa cavity (e.g., a cooling chamber) that is configured to receive coolingfluid (e.g., saline) when such cooling fluid is delivered and/orcirculated through the catheter or medical instrument.

In embodiments such as the one illustrated in FIG. 15, wherein no activefluid cooling is incorporated into the design of the catheter or othermedical instrument of the ablation system 2000, heat generated by and/orat the electrode (or other energy delivery member) 2030 can be moreevenly dissipated along the distal end of the catheter or medicalinstrument as a result of the heat dissipation properties of the heattransfer members 2050, including, without limitation, heat shuntmembers, (and/or the interior member 2070, to the extent that theinterior member 2070 also comprises favorable heat shunting properties,e.g., materials having favorable thermal diffusivity characteristics).Thus, the heat shunt members 2050 can help dissipate heat away from theelectrode or other energy delivery member (e.g., either via direct orindirect thermal contact with the electrode or other energy deliverymember) to reduce the likelihood of any localized hotspots (e.g., alongthe distal and/or proximal ends of the electrode or other energydelivery member). Accordingly, heat can be more evenly distributed withthe assistance of the heat shunt member 2050 along a greater volume,area and/or portion of the catheter. As discussed above, the use of heatshunting members can quickly and efficiently transfer heat away from theelectrode and the tissue being treated during use. The use of materialsthat comprises favorable thermal diffusivity properties can accomplishthe relatively rapid heat transfer without the negative effect of heatretention (e.g., which may otherwise cause charring, thrombus formationand/or other heat-related problems).

Further, in some embodiments, the flow of blood or other natural bodilyfluids of the subject in which the catheter or medical instrument ispositioned can facilitate with the removal of heat away from theelectrode or other energy delivery member. For example, the continuousflow of blood adjacent the exterior of the catheter during use can helpwith the removal of heat away from the distal end of the catheter. Suchheat transfer can be further enhanced or otherwise improved by thepresence of one or more heat shunt members that are in thermalcommunication with the exterior of the catheter. For example, in somearrangements, such as shown in FIG. 15, one or more heat shunt members2050 can extend to the exterior of the catheter or other medicalinstrument. Thus, as blood (and/or other bodily fluids) moves past thecatheter or other medical instrument when the catheter or medicalinstrument is inserted within the subject during use, heat can beadvantageously transferred through the heat shunt members 2050 to theblood and/or other bodily fluids moving adjacent the catheter. Again,the use of heat shunt materials with favorable thermal diffusivitycharacteristics will ensure that heat is not retained within suchmaterials, thereby creating a safer ablation system and treatmentprocedure.

FIGS. 16A and 16B illustrate another embodiment of a catheter or othermedical instrument of an ablation system 2100 that includes one or moreheat transfer members 2050 (e.g., heat shunt members) along and/or nearits distal end. Unlike other embodiments disclosed herein, theillustrated system includes a proximal electrode or electrode portion2130 that extends deeper into the interior of the catheter. For example,as depicted in the side cross-sectional view of FIG. 16B, the proximalelectrode 2130 can extend to or near the outside of the irrigationchannel 2120. As discussed herein, the irrigation channel 2120 cancomprise one or more metals, alloys and/or other rigid and/or semi-rigidmaterials, such as, for example, stainless steel.

With continued reference to FIGS. 16A and 16B, the proximal electrode orproximal electrode portion 2130 can be part of a composite (e.g.,split-tip) electrode system, in accordance with the various compositeembodiments disclosed herein. Thus, in some embodiments, in order forthe split tip electrode configuration to operate properly, the distalelectrode 2110 is electrically isolated from the proximal electrode2130. In the illustrated configuration, since the proximal electrode2130 extends to or near the metallic (and thus, electrically conductive)irrigation tube 2120, at least one electrically insulative layer,coating, member, portion, barrier and/or the like 2128 can beadvantageously positioned between the electrode 2130 and the irrigationtube 2120. In some embodiments, for example, the electrically insulativemember 2128 comprises one or more layers of polyimide, other polymericmaterial and/or another electrically insulative material, as desired orrequired. Such an electrically-insulative layer and/or other member 2128can take the place of diamond and/or another electrically-insulativeheat shunting member that may otherwise be positioned around theirrigation tube 2120 to electrically isolate the distal electrode 2110from the proximal electrode 2130.

According to any of the embodiments disclosed herein, the proximaland/or the distal electrodes 2130, 2110 can comprise one or more metalsand/or alloys. For example, the electrodes can include platinum,stainless steel and/or any other biocompatible metal and/or alloy. Thus,in some embodiments, the thicker proximal electrode 2130 that extends toor near the irrigation tube 2120 can be referred to as a “slug,” e.g.,“a platinum slug.” As discussed, in such arrangements, the need for aninternal diamond and/or other heat shunting member can be eliminated.Instead, in such embodiments, as depicted in FIG. 16B, the proximal anddistal ends of the “slug” or thicker proximal electrode 2130 can beplaced in thermal communication with one or more heat shunting members(e.g., diamond) to help shunt heat away from the electrode 2130 and/orthe tissue of the subject being treated. Thus, in some embodiments, theproximal and/or the distal faces of the proximal electrode or slug 2130can be placed in good thermal contact with adjacent heat shuntingmembers, as desired or required.

With continued reference to FIG. 16B, according to some embodiments, atleast a portion 2222 of the irrigation tube 2120 is perforated and/orhas one or more openings 2123. In some embodiments, such openings 2123can place an irrigation fluid carried within the interior of theirrigation channel 2120 in direct physical and thermal communicationwith an adjacent heat shunting member (e.g., diamond, Graphene, silica,etc.) to quickly and efficiently transfer heat away from the electrodeand/or tissue being treated. In some embodiments, the direct physicaland/or thermal communication between the irrigation fluid and theshunting member helps provide improved heat transfer to the irrigationfluid (e.g., saline) passing through the interior of the irrigationchannel 2120. In the illustrated embodiment, the openings 2123 along theperforated portion 2222 are generally circular in shape and evenlydistributed relative to each other (e.g., comprise a generally evendistribution or spacing relative to each other). However, in otherarrangements, the size, shape, spacing and/or other characteristics ofthe openings 2123 along the perforated or direct contact region 2122 ofthe channel 2120 can vary, as desired or required. For example, in someembodiments, the openings 2123 can be oval, polygonal (e.g., square orrectangular, triangular, pentagonal, hexagonal, octagonal, etc.),irregular and/or the like. In some embodiments, the openings are slottedor elongated.

Regardless of their exact shape, size, orientation, spacing and/or otherdetails, the openings 2123 that comprise the perforated or directcontact region 2122 of the channel 2120 can provide direct contactbetween the irrigation fluid and the adjacent diamond (and/or anotherheat shunting member) 1150 for 30% to 70% (e.g., 30-35, 35-40, 40-45,45-50, 50-55, 55-60, 60-65, 65-70%, percentages between the foregoingranges, etc.) of the surface area of the perforated or direct contactregion 2122 of the channel 2120. In other embodiments, the openings 2123that comprise the perforated or direct contact region 2122 of thechannel 2120 can provide direct contact between the irrigation fluid andthe adjacent diamond (and/or another heat shunting member) 2150 for lessthan 30% (e.g., 1-5, 5-10, 10-15, 15-20, 20-25, 25-30%, percentagesbetween the foregoing ranges, less than 1%, etc.) or greater than 70%(e.g., 70-75, 75-80, 80-85, 85-90, 90-95, 95-99%, percentages betweenthe foregoing ranges, greater than 99%, etc.) of the surface area of theperforated or direct contact region 2122 of the channel 2120, as desiredor required. Such a perforated or direct contact region 2122 can beincorporated into any of the embodiments disclosed herein. In addition,any of the embodiments disclosed herein, including, without limitation,the system of FIGS. 16A and 16B, can include more than one perforated ordirect contact region 2122. For example, the embodiment of FIGS. 16A and16B can include a second perforated or direct contact region along thedistal end of the proximal slug or electrode 2130 and/or along any otherportion adjacent a heat shunting member.

As illustrated in FIG. 16B, the distal end of an irrigation tube (e.g.,a flexible polyurethane or other polymeric conduit) 2104 that is influid communication with the irrigation channel 2120 that extendsthrough the distal end of the catheter or other medical instrument canbe positioned at least partially within an interior of such a channel2120. Such a configuration can be incorporated into any of theembodiments disclosed herein or variations thereof. In some embodiments,the distal portion of the irrigation tube 2104 can be sized, shapedand/or otherwise configured to press-fit within an interior of thedistal channel 2120. However, in some embodiments, one or more otherattachment devices or methods, such as, for example, adhesives, heatbonding, fasteners, etc., can be used to help secure the irrigation tube2104 to the irrigation channel 2120, as desired or required.

Another embodiment of a distal end of a catheter or other medicalinstrument 2200 comprising proximal and distal electrodes 2230, 2210 andheat shunting characteristics is illustrated in FIG. 16C. As shown, theproximal electrode or slug 2230 extends toward the interior of thecatheter (e.g., to or near the irrigation channel 2104, 2220). However,the depicted electrode 2230 is generally thinner than (e.g., does notextend as far as) the embodiment of FIGS. 16A and 16B. In theillustrated embodiment, one or more heating shunting members (e.g.,diamond, Graphene, silica, etc.) with favorable thermal diffusivitycharacteristics are positioned between the interior of the proximalelectrode or slug 2230 and the irrigation channel 2220. Thus, is such anarrangement, not only can heat generated at or along the electrode 2230and/or the tissue of the subject being treated be more quickly andefficiently transferred away from the electrode and/or tissue, but thediamond or other electrically-insulating heat shunting member or network2250 provides the necessary electrical insulation between the metallic(e.g., stainless steel) irrigation channel 2220 and the proximalelectrode or slug 2230. As noted herein, such electrical isolation ishelpful with a composite (e.g., split-tip) design.

A distal portion 2300 of another embodiment of an ablation system isillustrated in FIGS. 17A and 17B. As shown, the system comprises acomposite (e.g., split-tip) design, with a proximal electrode or slug2330 and a distal electrode 2310. Further, the catheter or other medicalinstrument includes one or more heat transfer members 2350, including,without limitation, a heat shunt network (e.g., comprising diamond,Graphene, silica and/or other materials with favorable thermaldiffusivity properties). According to some embodiments, as depicted inthe illustrated arrangement, the heat shunt network 2350 can includerings that extend to the exterior of the catheter or instrument and/orone or more interior members that are positioned within (e.g.,underneath) the proximal electrode 2330, as desired or required. Inaddition, as with other embodiments disclosed herein, one or moretemperature sensors 2392, 2394 can be provide along one or more portionsof the system (e.g., along or near the distal electrode 2310, along ornear the proximal heat shunt member, along or near the proximalelectrode 2330, etc.) to help detect the temperature of tissue beingtreated. As discussed in greater detail in such temperature sensors(e.g., thermocouples) can also be used to detect the orientation of thetip, to determine whether (and/or to what extent) contact is being madebetween the tip and tissue and/or the like.

With continued reference to the embodiment of FIGS. 17A and 17B, thecatheter or other medical instrument can include a proximal coupling ormember 2340. As shown, such a coupling or member 2340 is configured toconnect to and be placed in fluid communication with an irrigationconduit (e.g., polyurethane, other polymeric or other flexible conduit,etc.) 2304. For example, in the illustrated embodiment, the distal endof the irrigation conduit 2304 is sized, shaped and otherwise configuredto be inserted within a proximal end (e.g., recess) of the coupling2340. In some embodiments, the irrigation conduit 2304 is press-fitwithin the recess of the coupling 2340. In other arrangements, however,one or more other attachment devices or methods can be used to securethe conduit 2304 to the coupling 2340 (e.g., adhesive, weld, fasteners,etc.), either in lieu or in addition to a press-fit connection, asdesired or required. Regardless of the exact mechanism of securementbetween the irrigation conduit 2304 and the coupling 2340, fluid passingthrough the conduit 2304 can enter into a manifold 2342 of the coupling2340. In some embodiments, the manifold 2342 can divide the irrigationfluid flow into two or more pathways 2344. However, in some embodiments,the coupling 2340 does not have a manifold. For example, irrigationfluid entering the coupling 2340 can be routed only along a single fluidpathway, as desired or required.

In the embodiment of FIGS. 17A and 17B, the manifold (or other flowdividing feature, device or component) 2342 of the coupling 2340separates the irrigation flow into three different fluid pathways. Asshown, each such fluid pathway can be placed in fluid communication witha separate fluid conduit or sub-conduit 2320. In some embodiments, suchfluid conduits 2320 are equally spaced apart (e.g., radially) relativeto the centerline of the catheter or other medical instrument. Forexample, the conduits 2320 can be spaced apart at or approximately at120 degrees relative to each other. As shown, the conduits 2320 extend,at least partially, through the proximal heat shunt member 2350 and theproximal slug or electrode 2330. However, in other embodiments, theorientation, spacing and/or other details of the manifold 2342, 2344and/or the fluid conduits 2320 can vary. In addition, the number offluid conduits 2320 originating from the manifold system can be greaterthan 3 (e.g., 4, 5, 6, 7, greater than 7, etc.) or less than 3 (e.g., 1,2), as desired or required.

In some embodiments in which the system comprises an open-irrigationsystem, as illustrated in the longitudinal cross-sectional view of FIG.17B, one or more irrigation fluid outlets 2332 a, 2332 b, 2332 c can beprovided along one or more of the fluid conduits 2320. As shown, suchfluid outlets 2332 can provided within the proximal electrode 2330.However, in other embodiments, such outlets 2332 can be included withinone or more other portions of the system (e.g., a heat shunt member2350, the distal electrode 2310, etc.), either in lieu of or in additionto the proximal electrode 2330. Such a configuration (e.g., oneincluding a manifold and/or openings through the proximal electrode) canbe incorporated into any of the ablation system embodiments disclosedherein. As with other irrigation system arrangements disclosed herein,heat can be shunted (e.g., from the electrode, the tissue being treated,one or more other portions of the system, etc.) to the irrigation fluidpassing through the conduits and/or fluid outlets to help quickly andefficiently dissipate (e.g., shunt) heat from the system during use. Insome embodiments, as illustrated in FIGS. 17A and 17B, the relativesize, shape and/or other configuration of two or more of the fluidoutlets 2332 can vary. For example, in some arrangements, in order tobetter balance the fluid hydraulics of fluid passing through eachconduit 2320 (e.g., to better balance the flow rate passing through eachoutlet 2332), the proximal fluid outlets can be smaller than one or moreof the distal fluid outlets. However, in other embodiments, two or more(e.g., most or all) of the fluid outlets 2332 include the identicalshape, size and/or other properties.

In some embodiments, the orientation of the fluid outlets can be skewedrelative to the radial direction of the catheter or other medicalinstrument in which they are located. Such a skewing or offset can occurfor any fluid outlets located along the distal end of the catheter orother medical instrument (e.g., fluid outlets located along the distalelectrode as shown in FIGS. 13, 16A and 16B and 16C, fluid outletslocated along the proximal electrode as shown in FIGS. 17A and 17B,etc.). The extent to which the outlets are skewed or offset (e.g.,relative to the radial direction of the catheter or medical instrument,relative to a direction perpendicular to the longitudinal centerline ofthe catheter or medical instrument) can vary, as desired or required. Byway of example, the fluid openings can be skewed or offset relative tothe radial direction by 0 to 60 degrees (e.g., 0-5, 5-10, 10-15, 15-20,20-25, 25-30, 30-35, 35-40, 40-45, 45-50, 50-55, 55-60 degrees, anglesbetween the foregoing ranges, etc.). In some embodiments, the fluidopenings are skewed or offset relative to the radial direction by morethan 60 degrees (e.g., 60-65, 65-70, 70-75 degrees, angles between theforegoing ranges, greater than 70 degrees, etc.), as desired orrequired.

According to some embodiments, fluid outlets or openings located alongor near the distal electrode are skewed or offset distally (e.g., in adirection distal to the location of the corresponding fluid outlet oropening). In some embodiments, fluid outlets or openings located alongor near the proximal electrode are skewed or offset proximally (e.g., ina direction proximal to the location of the corresponding fluid outletor opening). Thus, in some embodiments, irrigation fluid exiting at ornear the distal electrodes is delivered in a direction distal to thecorresponding fluid outlet(s), and irrigation fluid exiting at or nearthe proximal electrodes is delivered in a direction proximal to thecorresponding fluid outlet(s). In some embodiments, such a configurationcan assist with cooling hot spots that may otherwise be created along ornear the electrode. Such a configuration could also help dilute theblood in those areas to help reduce the chance of thrombus and/orcoagulation formation.

Multiple Temperature Sensors

According to some embodiments, a medical instrument (e.g., ablationcatheter) can include multiple temperature-measurement devices (e.g.,thermocouples, thermistors, other temperature sensors) spaced axially atdifferent locations along a distal portion of the medical instrument.The axial spacing advantageously facilitates measurement of a meaningfulspatial temperature gradient. Each of the temperature-measurementdevices may be isolated from each of the other temperature-measurementdevices to provide independent temperature measurements. Thetemperature-measurement devices may be thermally and/or electricallyinsulated or isolated from one or more energy delivery members (e.g.,radiofrequency electrodes) so as not to directly measure the temperatureof the energy delivery member(s), thereby facilitating temperaturemeasurements that are isolated from the thermal effects of the energydelivery member(s). The medical instrument may comprise a firstplurality (e.g., set, array, group) of temperature-measurement devices(e.g., sensors) positioned at or adjacent a distal tip, or terminus, ofthe medical instrument (e.g., within a distal electrode portion of ahigh-resolution combination electrode assembly, or composite electrodeassembly). The first plurality of temperature-measurement devices may bespaced apart (e.g., circumferentially, radially) around the medicalinstrument along a first cross-sectional plane of the medicalinstrument, in an equidistant manner or non-equidistant manner. In oneembodiment, the first plurality of temperature-measurement devices ispositioned symmetrically around a longitudinal axis of the distal end ofthe medical instrument. The medical instrument may also comprise asecond plurality of temperature-measurement devices (e.g., sensors)spaced proximally from the first plurality of temperature-measurementdevices along a second cross-sectional plane of the medical instrumentthat is proximal of the first cross-sectional plane, thereby allowingfor temperature measurements to be obtained at multiple spaced-apartlocations. In some embodiments, the second plurality oftemperature-measurement devices is positioned adjacent to a proximal end(e.g., edge) of an electrode or other energy delivery member (if themedical instrument (e.g., ablation catheter) comprises a singleelectrode or other energy delivery member) or of the proximal-mostelectrode or other energy delivery member (if the medical instrumentcomprises multiple electrode members or other energy delivery members).

The temperature measurements obtained from the temperature-measurementdevices (e.g., sensors) may advantageously be used to determine, amongother things, an orientation of the distal tip of the medical instrumentwith respect to a tissue surface, an estimated temperature of a peaktemperature zone of a lesion formed by the medical instrument (e.g.,ablation catheter), and/or an estimated location of the peak temperaturezone of the lesion. In some embodiments, the determinations made usingthe temperature sensors or other temperature-measurement devices can beused to adjust treatment parameters (e.g., target temperature, power,duration, orientation) so as to prevent char or thrombus if used in ablood vessel and/or to control lesion parameters (e.g., depth, width,location of peak temperature zone, peak temperature), thus providingmore reliable and safer treatment (e.g., ablation) procedures.Accordingly, upon implementation of a control scheme that regulates thedelivery of power or other parameters to an energy delivery member(e.g., RF electrode, microwave emitter, ultrasound transducer, cryogenicemitter, other emitter, etc.) located along the distal end of a medicalapparatus (e.g., catheter, probe, etc.), the target level of treatmentcan be accomplished without negatively impacting (e.g., overheating,over-treating, etc.) the subject's tissue (e.g., within and/or adjacenta treatment volume).

The term peak temperature, as used herein, can include either a peak orhigh temperature (e.g., a positive peak temperature) or a trough or lowtemperature (e.g., negative peak temperature). As a result,determination of the peak temperature (e.g., maximum or minimumtemperature or other extreme temperature) within targeted tissue canresult in a safer, more efficient and more efficacious treatmentprocedure. In some embodiments, when, for example, cryoablation isperformed, the systems, devices and/or methods disclosed herein can beused to determine the trough or lowest temperature point, within thetreatment (e.g., ablation) volume. In some embodiments, technologiesthat cool tissue face similar clinical challenges of controlling thetissue temperature within an efficacious and safe temperature range.Consequently, the various embodiments disclosed herein can be used withtechnologies that either cool or heat targeted tissue.

Several embodiments of the invention are particularly advantageousbecause they include one, several or all of the following benefits: (i)reduction in proximal edge heating, (ii) reduced likelihood of char orthrombus formation, (iii) feedback that may be used to adjust ablationprocedures in real time, (iv) noninvasive temperature measurements, (v)determination of electrode-tissue orientation within a short time afterinitiation of energy delivery; (vi) safer and more reliable ablationprocedures; and (vii) tissue temperature monitoring and feedback duringirrigated or non-irrigated ablation.

For any of the embodiments disclosed herein, a catheter or otherminimally-invasive medical instrument can be delivered to the targetanatomical location of a subject (e.g., atrium, pulmonary veins, othercardiac location, renal artery, other vessel or lumen, etc.) using oneor more imaging technologies. Accordingly, any of the ablation systemsdisclosed herein can be configured to be used with (e.g., separatelyfrom or at least partially integrated with) an imaging device or system,such as, for example, fluoroscopy technologies, intracardiacechocardiography (“ICE”) technologies and/or the like. In someembodiments, energy delivery is substituted with fluid delivery (e.g.,hot fluid, cryogenic fluid, chemical agents) to accomplish treatment.

FIG. 18A illustrates a perspective view of a distal portion of anopen-irrigated ablation catheter 3120A comprising multipletemperature-measurement devices 3125, according to one embodiment. Asshown, the embodiment of the ablation catheter 3120A of FIG. 18A is anopen-irrigated catheter comprising a high-resolution combinationelectrode assembly, or composite (e.g., split-tip) electrode design. Thecomposite electrode design comprises a dome- or hemispherical-shapeddistal tip electrode member 3130, an insulation gap 3131 and a proximalelectrode member 3135. The ablation catheter 3120A comprises multipleirrigation ports 3140 and a thermal transfer member 3145 (e.g., heatshunt member).

The temperature-measurement devices 3125 comprise a first (e.g., distal)group of temperature-measurement devices 3125A positioned in recesses orapertures formed in the distal electrode member 3130 and a second (e.g.,proximal) group of temperature-measurement devices 3125B positioned inslots, notches or openings formed in the thermal transfer member 3145proximate or adjacent the proximal edge of the proximal electrode member3135. The temperature-measurement devices 3125 may comprisethermocouples, thermistors, fluoroptic sensors, resistive temperaturesensors and/or other temperature sensors. In various embodiments, thethermocouples comprise nickel alloy, platinum/rhodium alloy,tungsten/rhenium alloy, gold/iron alloy, noble metal alloy,platinum/molybdenum alloy, iridium/rhodium alloy, pure noble metal, TypeK, Type T, Type E, Type J, Type M, Type N, Type B, Type R, Type S, TypeC, Type D, Type G, and/or Type P thermocouples. A reference thermocouplemay be positioned at any location along the catheter 3120A (e.g., in ahandle or within a shaft or elongate member of the catheter 3120A). Inone embodiment, the reference thermocouple is thermally insulated and/orelectrically isolated from the electrode member(s). The electrodemember(s) may be substituted with other energy delivery members.

In some embodiments, the temperature-measurement devices are thermallyinsulated from the electrode members or portions 3130, 3135 so as toisolate the temperature measurements from the thermal effects of theelectrode members (e.g., to facilitate measurement of surroundingtemperature, such as tissue temperature, instead of measuringtemperature of the electrode members). As shown, thetemperature-measurement devices 3125 may protrude or extend outward froman outer surface of the ablation catheter 3120A. In some embodiments,the temperature-measurement devices 3125 may protrude up to about 1 mmaway from the outer surface (e.g., from about 0.1 mm to about 0.5 mm,from about 0.5 mm to about 1 mm, from about 0.6 mm to about 0.8 mm, fromabout 0.75 mm to about 1 mm, or overlapping ranges thereof). The domeshape of the distal tip electrode member 3130 and/or the outwardprotrusion or extension of the temperature-measurement devices 3125 mayadvantageously allow the temperature-measurement devices to be burieddeeper into tissue and away from effects of the open irrigation providedby irrigation ports 3140, in accordance with several embodiments. Theproximal group of temperature-measurement devices and the distal groupof temperature-measurement devices may protrude the same amount ordifferent amounts (as a group and/or individually within each group). Inother embodiments, the temperature-measurement devices 3125 are flush orembedded within the outer surface (e.g., 0.0 mm, −0.1 mm, −0.2 mm, −0.3mm, −0.4 mm, −0.5 mm from the outer surface) of an elongate body of themedical instrument. In some embodiments, the distaltemperature-measurement devices 3125A protrude or extend distally from adistal outer surface of the distal electrode member and the proximaltemperature-measurement devices 3125B are flush within a lateral outersurface of an elongate body of the ablation catheter 3120A.

With reference to FIG. 18D, a portion of the ablation catheter 3120Cwhere at least some of the temperature-measurement devices 3125 arepositioned may have a larger outer diameter or other outercross-sectional dimension than adjacent portions of the ablationcatheter 3120C so as to facilitate deeper burying of at least some ofthe temperature-measurement devices within tissue and to further isolatethe temperature measurements from the thermal effects of the electrodemembers or fluid (e.g., saline or blood). As shown in FIG. 18D, theportion of the ablation catheter 3120C comprising the proximal group oftemperature-measurement devices 3125B comprises a bulge, ring or ridge3155 having a larger outer diameter than adjacent portions.

In some embodiments, the temperature-measurement devices 3125 areadapted to be advanced outward and retracted inward. For example, thetemperature-measurement devices 3125 may be in a retracted position(within the outer surface or slightly protruding outward) duringinsertion of the ablation catheter and movement to the treatmentlocation to reduce the outer profile and facilitate insertion to thetreatment location and may be advanced outward when at the treatmentlocation. The features described above in connection with ablationcatheter 3120C of FIG. 18D may be employed with any of the otherablation catheters described herein.

Returning to FIG. 18A, the proximal and distal groups oftemperature-measurement devices 3125 may each comprise or consist oftwo, three, four, five, six, or more than six temperature-measurementdevices. In the illustrated embodiment, the proximal and distal groupsof temperature-measurement devices 3125 each consist of threetemperature-measurement devices, which may provide a balance betweenvolumetric coverage and reduced number of components. The number oftemperature-measurement devices 3125 may be selected to balanceaccuracy, complexity, volumetric coverage, variation in tip to tissueapposition, cost, number of components, and/or size constraints. Asshown in FIG. 18A, the temperature-measurement devices 3125 may beequally spaced apart around a circumference of the ablation catheter3120A or spaced an equal number of degrees apart from each other (e.g.,symmetrically) about a central longitudinal axis extending from aproximal end to a distal end of the ablation catheter. For example, whenthree temperature-measurement devices are used, they may be spaced about120 degrees apart and when four temperature-measurement devices areused, they may be spaced about 90 degrees apart. In other embodiments,the temperature-measurement devices 3125 are not spaced apart equally.

As shown in the embodiment of FIG. 18A, the temperature-measurementdevices 3125 of each group may be positioned along the samecross-sectional plane (e.g., are co-planar) of the ablation catheter3120A. For example, the distal temperature-measurement devices 3125A maybe positioned to extend the same distance outward from the dome-shapedsurface and the proximal temperature-measurement devices 3125B may eachbe spaced the same distance from the distal tip of the ablation catheter3120A. As shown in the embodiment of FIG. 18A, the distaltemperature-measurement devices 3125A extend from a distal outer surfaceof the distal electrode member in an axial direction that is parallel orsubstantially parallel with a central longitudinal axis of the distalportion of the ablation catheter 3120A and the proximaltemperature-measurement devices 3125B extend radially outward from theouter surface of the ablation catheter 3120A. In other embodiments, thedistal temperature-measurement devices 3125A may not be positioned in oron the distal outer surface of the distal terminus but may be positionedon a lateral surface to extend radially outward (similar to theillustrated proximal temperature-measurement devices 3125B). In someembodiments, the temperature-measurement devices 3125 are not spacedapart in two separated groups of co-planar temperature-measurementdevices within each group but are otherwise spatially distributed.

As shown in the embodiment of FIG. 18A, the distaltemperature-measurement devices 3125A may be positioned distal of theinsulation gap 3131 and/or of the irrigation ports 3140 and the proximaltemperature-measurement devices 3125B may be positioned proximal to theproximal edge of the proximal electrode member 3135 within the thermaltransfer member 3145. In other embodiments, the proximaltemperature-measurement devices 3125B may be positioned distal to theproximal edge of the proximal electrode member 3135 (e.g., withinrecesses or apertures formed within the proximal electrode member 3135similar to the recesses or apertures formed in the distal tip electrodemember illustrated in FIG. 18A). In other embodiments, the distaltemperature-measurement devices 3125A and/or the proximaltemperature-measurement devices 3125B may be positioned at otherlocations along the length of the ablation catheter 3120A. In someembodiments, each distal temperature-measurement device 3125A is axiallyaligned with one of the proximal temperature-measurement devices 3125Band the spacing between the distal temperature-measurement devices 3125Aand the proximal temperature-measurement devices is uniform orsubstantially uniform.

The irrigation ports 3140 may be spaced apart (equidistant or otherwise)around a circumference of the shaft of the ablation catheter 3120A. Theirrigation ports 3140 are in communication with a fluid source, such asa fluid source provided by the irrigation fluid system 70 of FIG. 1. Theirrigation ports facilitate open irrigation and provide cooling to theelectrode members 3130, 3135 and any blood surrounding the electrodemembers 3130, 3135. In some embodiments, the ablation catheter 3120Acomprises three, four, five, six, seven, eight or more than eight exitports 3140. In various embodiments, the exit ports 3140 are spacedbetween 0.005 and 0.015 inches from the proximal edge of the distalelectrode member 3130 so as to provide improved cooling of the thermaltransfer member 3145 at the tissue interface; however, other spacing canbe used as desired and/or required. In other embodiments, the exit ports3140 are spaced apart linearly and/or circumferentially along theproximal electrode member 3135 (as shown, for example, in FIG. 18E).

FIGS. 18B and 18C illustrate a perspective view and a cross-sectionalview, respectively, of a distal portion of an open-irrigated ablationcatheter 3120B having multiple temperature-measurement devices,according to another embodiment. The ablation catheter 3120B may includeany or all of the structural components, elements and features of theablation catheter 3120A described above and ablation catheter 3120A mayinclude any or all of the structural components, elements and featuresdescribed in connection with FIGS. 18B and 18C. The ablation catheter3120B comprises a flat tip electrode member 3130 instead of adome-shaped tip electrode member as shown in FIG. 18A. In other words,the distal outer surface is planar or flat instead of rounded orhemispherical. In accordance with several embodiments, the distaltemperature-measurement devices 3125A are positioned in or on the flator planar surface and not on a curved, toroidal or radiused surface ofthe distal tip electrode member connecting the distal outer surface anda lateral outer surface of the distal tip electrode member.

As best shown in FIG. 18C, the thermal transfer member 3145 is inthermal contact with one or both of the electrode members 3130, 3135.The thermal transfer member 3145 can extend to, near or beyond theproximal end of the proximal electrode member 3135. In some embodiments,the thermal transfer member 3145 terminates at or near the proximal endof the proximal electrode member 3135. However, in other arrangements(as shown in FIG. 18C), the thermal transfer member 3145 extends beyondthe proximal end of the proximal electrode member 3135. In yet otherembodiments, the thermal transfer member 3145 terminates distal of theproximal end (e.g., edge) of the proximal electrode member 3135. Thethermal transfer member 3145 may extend from the proximal surface of thetip electrode member 3130 to a location beyond the proximal end of theproximal electrode member 3135. Embodiments wherein the thermal transfermember 3145 extends beyond the proximal end of the proximal electrodemember 3135 may provide increased shunting of proximal edge heatingeffects caused by the increased amount of current concentration at theproximal edge by reducing the heat at the proximal edge throughconductive cooling. In some embodiments, at least a portion of thethermal transfer member 3145 is in direct contact with the tissue (e.g.,within insulation gap 3131) and can remove or dissipate heat directlyfrom the targeted tissue being heated.

The thermal transfer member 3145 can comprise one or more materials thatinclude favorable heat transfer properties. For example, in someembodiments, the thermal conductivity of the material(s) included in thethermal transfer member is greater than 300 W/m/° C. (e.g., 300-350,350-400, 400-450, 450-500, 500-600, 600-700 W/m/° C., ranges between theforegoing, greater than 700 W/m/° C., etc.). Possible materials withfavorable thermal conductivity properties include, but are not limitedto, copper, brass, beryllium, other metals and/or alloys, aluminalceramics, other ceramics, industrial diamond and/or other metallicand/or non-metallic materials.

According to certain embodiments where the heat transfer memberscomprise heat shunting members, the thermal diffusivity of thematerial(s) included in the heat shunt members and/or of the overallheat shunt assembly (e.g., when viewed as a unitary member or structure)is greater than 1.5 cm²/sec (e.g., 1.5-2, 2-2.5, 2.5-3, 3-4, 4-5, 5-6,6-7, 7-8, 8-9, 9-0, 10-11, 11-12, 12-13, 13-14, 14-15, 15-20 cm²/sec,values between the foregoing ranges, greater than 20 cm²/sec). Thermaldiffusivity measures the ability of a material to conduct thermal energyrelative to its ability to store thermal energy. Thus, even though amaterial can be efficient as transferring heat (e.g., can have arelatively high thermal conductivity), it may not have favorable thermaldiffusivity properties, because of its heat storage properties. Heatshunting, unlike heat transferring, requires the use of materials thatpossess high thermal conductance properties (e.g., to quickly transferheat through a mass or volume) and a low heat capacity (e.g., to notstore heat). Possible materials with favorable thermal diffusivity, andthus favorable heat shunting properties, include, but are not limitedto, industrial diamond, graphene, silica alloys, ceramics, othercarbon-based materials and/or other metallic and/or non-metallicmaterials. In various embodiments, the material used for the heattransfer (e.g., diamond) provides increased visibility of the cathetertip using ICE imaging or other imaging techniques.

The use of materials with favorable thermal diffusivity properties canhelp ensure that heat can be efficiently transferred away from theelectrode and/or the adjacent tissue during a treatment procedure. Incontrast, materials that have favorable thermal conductivity properties,but not favorable thermal diffusivity properties, such as, for example,copper, other metals or alloys, thermally conductive polypropylene orother polymers, etc., will tend to retain heat. As a result, the use ofsuch materials that store heat may cause the temperature along theelectrode and/or the tissue being treated to be maintained at anundesirably elevated level (e.g., over 75 degrees C.) especially overthe course of a relatively long ablation procedure, which may result incharring, thrombus formation and/or other heat-related problems.

Industrial diamond and other materials with the requisite thermaldiffusivity properties for use in a thermal shunting network, asdisclosed in the various embodiments herein, comprise favorable thermalconduction characteristics. Such favorable thermal conduction aspectsemanate from a relatively high thermal conductance value and the mannerin which the heat shunt members of a network are arranged with respectto each other within the tip and with respect to the tissue. Forexample, in some embodiments, as radiofrequency energy is emitted fromthe tip and the ohmic heating within the tissue generates heat, theexposed distal most shunt member (e.g., located 0.5 mm from the distalmost end of the tip) can actively extract heat from the lesion site. Thethermal energy can advantageously transfer through the shunting networkin a relatively rapid manner and dissipate through the shunt residingbeneath the radiofrequency electrode surface the heat shunt network,through a proximal shunt member and/or into the ambient surroundings.Heat that is shunting through an interior shunt member can be quicklytransferred to an irrigation conduit extending through an interior ofthe catheter or other medical instrument. In other embodiments, heatgenerated by an ablation procedure can be shunted through both proximaland distal shunt members (e.g., shunt members that are exposed to anexterior of the catheter or other medical instrument, such as shown inmany of the embodiments herein).

Further, as noted above, the materials with favorable thermaldiffusivity properties for use in a heat shunt network not only have therequisite thermal conductivity properties but also have sufficiently lowheat capacity values. This helps ensure that the thermal energy isdissipated very quickly from the tip to tissue interface as well as thehot spots on the electrode, without heat retention in the heat shuntingnetwork. The thermal conduction constitutes the primary heat dissipationmechanism that ensures quick and efficient cooling of the tissue surfaceand of the radiofrequency electrode surface. Conversely a heat transfer(e.g., with relatively high thermal conductivity characteristics butalso relatively high heat capacity characteristics) will store thermalenergy. Over the course of a long ablation procedure, such stored heatmay exceed 75 degrees Celsius. Under such circumstances, thrombus and/orchar formation can undesirably occur.

The thermal convection aspects of the various embodiments disclosedherein two-fold. First, an irrigation lumen of the catheter can absorbthermal energy which is transferred to it through the shunt network.Such thermal energy can then be flushed out of the distal end of theelectrode tip via the irrigation ports. In closed irrigation systems,however, such thermal energy can be transferred back to a proximal endof the catheter where it can be removed. Second, the exposed shuntsurfaces along an exterior of the catheter or other medical instrumentcan further assist with the dissipation of heat from the electrodeand/or the tissue being treated. For example, such heat dissipation canbe accomplished via the inherent convective cooling aspects of the bloodflowing over the surfaces of the electrode.

Accordingly, the use of materials in a heat shunting network withfavorable thermal diffusivity properties, such as industrial diamond,can help ensure that heat is quickly and efficiently transferred awayfrom the electrode and treated tissue, while maintaining the heatshunting network cool (e.g., due to its low heat capacity properties).This can create a safer ablation catheter and related treatment method,as potentially dangerous heat will not be introduced into the procedurevia the heat shunting network itself.

In some embodiments, the heat shunt members disclosed herein draw outheat from the tissue being ablated and shunt it into the irrigationchannel. Similarly, heat is drawn away from the potential hot spots thatform at the edges of electrodes and are shunted through the heat shuntnetwork into the irrigation channel. From the irrigation channel, viaconvective cooling, heat can be advantageously released into the bloodstream and dissipated away. In closed irrigation systems, heat can beremoved from the system without expelling irrigation fluid into thesubject.

According to some embodiments, the various heat shunting systemsdisclosed herein rely on heat conduction as the primary coolingmechanism. Therefore, such embodiments do not require a vast majority ofthe heat shunting network to extend to an external surface of thecatheter or other medical instrument (e.g., for direct exposure to bloodflow). In fact, in some embodiments, the entire shunt network can residewithin an interior of the catheter tip (i.e., with no portion of theheat shut network extending to an exterior of the catheter or othermedical instrument). Further, the various embodiments disclosed hereindo not require electrical isolation of the heat shunts from theelectrode member or from the irrigation channel.

As shown in FIG. 18C, the thermal transfer member 3145 is also inthermal contact with a heat exchange chamber (e.g., irrigation conduit)3150 extending along an interior lumen of the ablation catheter 3120B.For any of the embodiments disclosed herein, at least a portion of athermal transfer member (e.g., heat shunt member) that is in thermalcommunication with the heat exchange chamber 3150 extends to an exteriorsurface of the catheter, adjacent to (and, in some embodiments, inphysical and/or thermal contact with) one or more electrodes or otherenergy delivery members. Such a configuration, can further enhance thecooling of the electrode(s) or other energy delivery member(s) when thesystem is activated, especially at or near the proximal end of theelectrode(s) or energy delivery member(s), where heat may otherwise tendto be more concentrated (e.g., relative to other portions of theelectrode or other energy delivery member). According to someembodiments, thermal conductive grease and/or any other thermallyconductive material (e.g., thermally-conductive liquid or other fluid,layer, member, coating and/or portion) can be used to place the thermaltransfer member 3145 in thermal communication with the heat exchangechamber (e.g., irrigation conduit) 3150, as desired or required. In suchembodiments, such a thermally conductive material places the electrodemembers 3130, 3135 in thermal communication, at least partially, withthe irrigation conduit 3150.

The irrigation conduit(s) 3150 can be part of an open irrigation system,in which fluid exits through the exit ports or openings 3140 along thedistal end of the catheter (e.g., at or near the electrode member 3130)to cool the electrode members and/or the adjacent targeted tissue. Invarious embodiments, the irrigation conduit 3150 comprises one or moremetallic and/or other favorable heat transfer (e.g., heat shunting)materials (e.g., copper, stainless steel, other metals or alloys,ceramics, polymeric and/or other materials with relatively favorableheat transfer properties, etc.). The irrigation conduit 3150 can extendbeyond the proximal end of the proximal electrode member 3135 and intothe proximal portion of the thermal transfer member 3145. The inner wallof the irrigation conduit 3150 may comprise a biocompatible material(such as stainless steel) that forms a strong weld or bond between theirrigation conduit 3150 and the material of the electrode member(s).

In some embodiments, the ablation catheters 3120 only compriseirrigation exit openings 3140 along a distal end of the catheter (e.g.,along a distal end of the distal electrode member 3130). In someembodiments, the system does not comprise any irrigation openings alongthe thermal transfer member 3145.

The thermal transfer member 3145 may advantageously facilitate thermalconduction away from the electrode members 3130, 3135, thereby furthercooling the electrode members 3130, 3135 and reducing the likelihood ofchar or thrombus formation if the electrode members are in contact withblood. The thermal transfer member 3145 may provide enhanced cooling ofthe electrode members 3130, 3135 by facilitating convective heattransfer in connection with the irrigation conduit 3150 in addition tothermal conduction.

Heat transfer (e.g., heat shunting) between the thermal transfer member3145 and the electrode members 3130, 3135 can be facilitated andotherwise enhanced by eliminating air gaps or other similar spacesbetween the electrode members and the thermal transfer member. Forexample, one or more layers of an electrically conductive material(e.g., platinum, gold, other metals or alloys, etc.) may be positionedbetween the interior of the electrode member and the exterior of thethermal transfer member 3145. Such layer(s) can be continuously orintermittently applied between the electrode member (or another type ofablation member) and the adjacent thermal transfer member. Further, suchlayer(s) can be applied using one or more methods or procedures, suchas, for example, sputtering, other plating techniques and/or the like.Such layer(s) can be used in any of the embodiments disclosed herein orvariations thereof. In addition, the use of a heat shunting networkspecifically can help transfer heat away from the tissue being treatedby the electrode member(s) without itself absorbing heat.

In some embodiments, the ablation catheter 3120 comprises multiplethermal transfer members 3145 (e.g., heat shunt disks or members). Forexample, according to some embodiments, such additional heat transfermembers may be positioned proximal of thermal transfer member 3145 andmay comprise one or more fins, pins and/or other members that are inthermal communication with the irrigation conduit 3150 extending throughan interior of the ablation catheter. Accordingly, as with the thermaltransfer members 3145 positioned in contact with the electrode members3130, 3135 heat can be transferred and thus removed or dissipated, fromother energy delivery members or electrodes, the adjacent portions ofthe catheter and/or the adjacent tissue of the subject via theseadditional heat transfer members (e.g., heat shunting members). In otherembodiments, ablation catheters do not comprise any thermal transfermembers.

In some embodiments, for any of the ablation catheters disclosed hereinor variations thereof, one or more of the thermal transfer members(e.g., heat shunting members) that facilitate the heat transfer to aheat exchange chamber (e.g., irrigation conduit) of the catheter are indirect contact with the electrode members and/or the heat exchangechamber. However, in other embodiments, one or more of the thermaltransfer members do not contact the electrode members and/or theirrigation conduit. Thus, in such embodiments, the thermal transfermembers are in thermal communication with the electrode members orsingle electrode and/or irrigation conduit, but not in physical contactwith such components. For example, in some embodiments, one or moreintermediate components, layers, coatings and/or other members arepositioned between a thermal transfer member (e.g., heat shuntingmember) and the electrode (or other ablation member) and/or theirrigation conduit. In some embodiments, irrigation is not used at alldue to the efficiency of the thermal transfer members. For example,where multiple levels or stacks of thermal transfers are used, the heatmay be dissipated over a larger area along the length of the ablationcatheter. Additional details regarding function and features of thermaltransfer members (e.g., heat shunting members) are provided herein. Thefeatures of the various embodiments disclosed therein (e.g., of thermalshunt systems and members) may be implemented in any of the embodimentsof the medical instruments (e.g., ablation catheters) disclosed herein.

As best shown in FIGS. 18C, 18E and 18F, the temperature-measurementdevices 3125 are thermally insulated from the electrode members 3130,3135 by tubing 3160 and/or air gaps. In some embodiments, the tubing3160 extends along an entire length (and beyond in some embodiments) ofthe electrode members 3130, 3135 such that no portion of the electrodemember is in contact with the temperature-measurement devices 3125,thereby isolating the temperature measurements from the thermal effectsof the electrode members. The outer tubing 3160 of thetemperature-measurement devices may comprise an insulating materialhaving low thermal conductivity (e.g., polyimide, ULTEM™, polystyrene orother materials having a thermal conductivity of less than about 0.5W/m/° K). The tubing 3160 is substantially filled with air or anothergas having very low thermal conductivity. The distal tip 3165 of thetemperature-measurement device (e.g., the portion where the temperatureis sensed) may comprise an epoxy polymer covering or casing filled witha highly conductive medium (e.g., nanotubes comprised of graphene,carbon or other highly thermally conductive materials or films) toincrease thermal conduction at a head of the temperature-measurementdevice where temperature is measured. In some embodiments, the distaltip 3165 comprises an epoxy cap having a thermal conductivity that is atleast 1.0 W/m/° K. The epoxy may comprise metallic paste (e.g.,containing aluminum oxide) to provide the enhanced thermal conductivity.In some embodiments, the distal tip 3165 or cap creates an isothermalcondition around the temperature-measurement device 3125 that is closeto the actual temperature of tissue in contact with thetemperature-measurement device. Because the distal tip 3165 of eachtemperature-measurement device 3125 is isolated from thermal conductivecontact with the electrode member(s), it retains this isothermalcondition, thereby preventing or reducing the likelihood of dissipationby the thermal mass of the electrode member(s). FIGS. 18E and 18Fillustrate a perspective view and a cross-sectional view, respectively,of a distal portion of an ablation catheter showing isolation of thedistal temperature-measurement devices from an electrode tip, accordingto one embodiment. As shown, the distal temperature measurement devices3125A may be surrounded by air gaps or pockets 3162 and/or insulation.The outer tubing 3160 may comprise an insulation sleeve that extendsalong the entire length, or at least a portion of the length, of thedistal electrode member 3130. The sleeve may extend beyond the distalelectrode member 3130 or even to or beyond the proximal electrode member3135.

The electrode member(s) (e.g., the distal electrode member 3130) can beelectrically coupled to an energy delivery module (e.g., energy deliverymodule 40 of FIG. 1). As discussed herein, the energy delivery module 40can comprise one or more components or features, such as, for example,an energy generation device 42 that is configured to selectivelyenergize and/or otherwise activate the energy delivery members (e.g., RFelectrodes), one or more input/output devices or components, one or moreprocessors (e.g., one or more processing devices or control units) thatare configured to regulate one or more aspects of the treatment system,a memory and/or the like. Further, such a module can be configured to beoperated manually or automatically, as desired or required.

The temperature-measurement devices 3125 can be coupled to one or moreconductors (e.g., wires, cables, etc.) that extend along the length ofthe ablation catheter 3120 and communicate the temperature signals backto at least one processing device (e.g., processor 46 of FIG. 1) fordetermining temperature measurements for each of thetemperature-measurement devices, as will be discussed in greater detailbelow.

According to some embodiments, the relative length of the differentelectrodes or electrode members 3130, 3135 can vary. For example, thelength of the proximal electrode member 3135 can be between 1 to 20times (e.g., 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12,12-13, 13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20, values betweenthe foregoing ranges, etc.) the length of the distal electrode member3130, as desired or required. In yet other embodiments, the lengths ofthe distal and proximal electrode members 3130, 3135 are about equal. Insome embodiments, the distal electrode member 3130 is longer than theproximal electrode member 3135 (e.g., by 1 to 20 times, such as, forexample, 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12,12-13, 13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20, values betweenthe foregoing ranges, etc.).

In some embodiments, the distal electrode member 3130 is 0.5 mm long. Inother embodiments, the distal electrode member 3130 is between 0.1 mmand 1 mm long (e.g., 0.1-0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6,0.6-0.7, 0-0.8, 0.7-0.8, 0.8-0.9, 0.9-1 mm, values between the foregoingranges, etc.). In other embodiments, the distal electrode member 3130 isgreater than 1 mm in length, as desired or required. In someembodiments, the proximal electrode member 3135 is 2 to 4 mm long (e.g.,2-2.5, 2.5-3, 3-3.5, 3.5-4 mm, lengths between the foregoing, etc.).However, in other embodiments, the proximal electrode member 3135 isgreater than 4 mm (e.g., 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 mm, greater than10 mm, etc.) or smaller than 1 mm (e.g., 0.1-0.5 0.5-1, 1-1.5, 1.5-2 mm,lengths between the foregoing ranges, etc.), as desired or required. Inembodiments where the split electrodes are located on catheter shafts,the length of the electrode members can be 1 to 5 mm (e.g., 1-2, 2-3,3-4, 4-5 mm, lengths between the foregoing, etc.). However, in otherembodiments, the electrode members can be longer than 5 mm (e.g., 5-6,6-7, 7-8, 8-9, 9-10, 10-15, 15-20 mm, lengths between the foregoing,lengths greater than 20 mm, etc.), as desired or required.

The electrode member(s) may be energized using one or more conductors(e.g., wires, cables, etc.). For example, in some arrangements, theexterior of the irrigation conduit 3150 comprises and/or is otherwisecoated with one or more electrically conductive materials (e.g., copper,other metal, etc.). Thus, the conductor can be placed in contact withsuch a conductive surface or portion of the irrigation conduit 3150 toelectrically couple the electrode member(s) to an energy deliverymodule. However, one or more other devices and/or methods of placing theelectrode member(s) in electrical communication with an energy deliverymodule can be used. For example, one or more wires, cables and/or otherconductors can directly or indirectly couple to the electrode member(s),without the use of the irrigation conduit.

The use of a composite tip (e.g., split tip) design can permit a user tosimultaneously ablate or otherwise thermally treat targeted tissue andmap (e.g., using high-resolution mapping) in a single configuration.Thus, such systems can advantageously permit precise high-resolutionmapping (e.g., to confirm that a desired level of treatment occurred)during a procedure. In some embodiments, the composite tip (e.g., splittip) design that includes two electrode members or electrode portions3130, 3135 can be used to record a high-resolution bipolar electrogram.For such purposes, the two electrodes or electrode portions can beconnected to the inputs of an electrophysiology (EP) recorder. In someembodiments, a relatively small separation distance (e.g., gap G)between the electrode members or electrode portions 3130, 3135 enableshigh-resolution mapping. According to some arrangements, thecomposite-tip electrode embodiments disclosed herein are configured toprovide localized high-resolution electrograms (e.g., electrogramshaving a highly increased local specificity as a result of theseparation of the two electrode portions and a high thermal diffusivityof the material of the separator, such as industrial diamond). Theincreased local specificity may cause the electrograms to be moreresponsive to electrophysiological changes in underlying cardiac tissueor other tissue so that effects that RF energy delivery has on cardiactissue or other tissue may be seen more rapidly and more accurately onthe high-resolution electrograms.

In some embodiments, a medical instrument (e.g., a catheter) 3120 caninclude three or more electrode members or electrode portions (e.g.,separated by gaps), as desired or required. According to someembodiments, regardless of how many electrodes or electrode portions arepositioned along a catheter tip, the electrode members or electrodeportions 3130, 3135 are radiofrequency electrodes and comprise one ormore metals, such as, for example, stainless steel, platinum,platinum-iridium, gold, gold-plated alloys and/or the like.

According to some embodiments, the electrode members or electrodeportions 3130, 3135 are spaced apart from each other (e.g.,longitudinally or axially) using the gap (e.g., an electricallyinsulating gap) 3131. In some embodiments, the length of the gap 3131(or the separation distance between adjacent electrode members orelectrode portions) is 0.5 mm. In other embodiments, the gap orseparation distance is greater or smaller than 0.5 mm, such as, forexample, 0.1-1 mm (e.g., 0.1-0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5, 0.5-0.6,0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0 mm, values between the foregoingranges, less than 0.1 mm, greater than 1 mm, etc.), as desired orrequired.

According to some embodiments, a separator is positioned within the gap3131 between the adjacent electrode members or electrode portions 3130,3135. The separator can comprise one or more electrically insulatingmaterials, such as, for example, Teflon, polyetheretherketone (PEEK),diamond, epoxy, polyetherimide resins (e.g., ULTEM™), ceramic materials,polyimide and the like. As shown in FIGS. 18A-18C and 19A-19C, theseparator may comprise a portion of the thermal transfer member 3145extending within the gap 3131.

As noted above with respect to the gap 3131 separating the adjacentelectrode members or electrode portions, the insulating separator can be0.5 mm long. In other embodiments, the length of the separator can begreater or smaller than 0.5 mm (e.g., 0.1-0.2, 0.2-0.3, 0.3-0.4,0.4-0.5, 0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0 mm, values betweenthe foregoing ranges, less than 0.1 mm, greater than 1 mm, etc.), asdesired or required.

According to some embodiments, to ablate or otherwise heat or treattargeted tissue of a subject successfully with the split tip electrodedesign, such as the ones depicted in FIGS. 18A-18C and 19A-19C, the twoelectrode members or electrode portions 3130, 3135 are electricallycoupled to each other at the RF frequency. Thus, the two electrodemembers or electrode portions can advantageously function as a singlelonger electrode at the RF frequency. Additional details regardingfunction and features of a composite (e.g., split tip) electrode designare provided herein.

FIGS. 19A-19C illustrate a distal portion of closed-irrigation ablationcatheters 3220 having multiple temperature-measurement devices 3225,according to various embodiments. The embodiment of the ablationcatheter 3220A of FIG. 19A comprises a dome-shaped tip electrode member3230 similar to the ablation catheter 3120A of FIG. 18A. The embodimentof the ablation catheter 3220B of FIGS. 19B and 19C comprises a flat tipelectrode member similar to the ablation catheter 3120B of FIGS. 18B and18C. The ablation catheters 3220A and 3220B include similar componentsand features as those described above in connection with FIGS. 18A-18C.For example, temperature-measurement devices 3225 correspond totemperature-measurement devices 3125, electrode members 3230, 3235correspond to electrode members 3130, 3135, thermal transfer member 3245corresponds to thermal transfer member 3145 and irrigation conduit 3250corresponds to irrigation conduit 3150. Accordingly, these features willnot be described again in connection with FIGS. 19A-19C. The ablationcatheter 3220 does not include irrigation ports because it operates as aclosed irrigation device.

The ablation catheter 3220 comprises two lumens 3265 within theirrigation conduit 3250, an inlet lumen (e.g., fluid delivery channel)3265A and an outlet lumen (e.g., return channel) 3265B. As illustratedin the cross-sectional view of FIG. 19C, the outlet of the inlet lumen3265A and the inlet of the outlet lumen 3265B terminate at spaced-apartlocations within the irrigation conduit 3250. The outlet of the inletlumen 3265A terminates within the distal electrode member 3230 oradjacent to a proximal end surface of the distal electrode member 3230.The inlet of the outlet lumen terminates proximal to the proximal end ofthe proximal electrode member 3235. The offset spacing of the distalends of the lumens 3265 advantageously induces turbulence, vortexing orother circulating fluid motions or paths within the irrigation conduit,thereby facilitating enhanced cooling by circulating the fluid toconstantly refresh or exchange the fluid in contact with the thermaltransfer member 3245 and/or electrode members.

In accordance with several embodiments, ablation catheters havingmultiple temperature-measurement devices do not require a composite(e.g., split-tip) electrode design and/or thermal transfer members. FIG.19D illustrates a perspective view of a distal portion of anopen-irrigated ablation catheter 3320 that does not include a compositeelectrode design or a thermal transfer member. The ablation catheter3320 comprises a first (e.g., distal) plurality oftemperature-measurement devices 3325A and a second (e.g., proximal)plurality of temperature-measurement devices 3325B. Thetemperature-measurement devices 3325 comprise similar features,properties, materials, elements and functions as thetemperature-measurement devices 3125, 3225 (FIGS. 18A-19C). The ablationcatheter 3320 may comprise or consist of a single unitary tip electrode3330. The tip electrode 3330 may comprise apertures, slots, grooves,bores or openings for the temperature-measurement devices 3325 at theirrespective spaced-apart locations. As shown in FIG. 19D, the proximaltemperature-measurement devices 3325B are positioned distal but adjacentto the proximal edge of the tip electrode 3330. The proximaltemperature-measurement devices 3325B could be positioned within 1 mm ofthe proximal edge (e.g., within 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2,0.1 mm proximal or distal of the proximal edge, depending on the lengthof the tip electrode 3330). In other embodiments, the proximaltemperature-measurement devices 3325B are positioned proximal of theproximal edge of the tip electrode 3330 and within the same distance asdescribed above of distal placement. In various embodiments, thetemperature-measurement devices are positioned at or near the proximaland distal edges of the electrode or composite (e.g., split-tip)electrode assembly because those locations tend to be the hottest. Basedon manufacturing tolerances, these temperature measurement devices maybe embedded at the proximal or distal edge of the tip electrode 3330.Accordingly, positioning of the temperature-measurement devices at ornear these locations may facilitate prevention, or reduced likelihood,of overheating or char or thrombus formation. Additionally, suchtemperature-measurement device placement offers the ability to monitortissue temperature during irrigated ablation.

In some embodiments, epoxy comprising a conductive medium (such asgraphene or other carbon nanotubes) may be blended in to the distaltubing (typically formed of plastic) of the ablation catheter shaft andthe distal tubing of the ablation catheter itself may function as athermal transfer. In some embodiments, the addition of the conductiveepoxy could increase the thermal conductivity of the distal tubing by2-3 times or more. These conductive tubing features and other featuresdescribed in connection with FIG. 19D may be used in connection with theablation catheters 3120, 3220 as well.

In certain embodiments, the heat shunt members included along the distalend of the catheter or other medical instrument are maintained within aninterior of such a catheter or medical instrument. In some embodiments,this is accomplished by providing one or more layers or coatingspartially or completely along the exterior or outer surfaces of heatshunt portions. Such layers or coatings can be electrically insulative.Further, in some arrangements, such layers or coatings can be bothelectrically-insulative and thermally-insulative, as desired orrequired. However, in other embodiments, the layers or coatings can beelectrically insulative but not thermally insulative. As used herein,electrically insulative means having an electrical resistivity in excessof 1000 Ω·cm. Further, as used herein, thermally conductive means havinga thermal conductivity greater than 0.5 W/cm-K at 20° C.

Embodiments that include such layers or coatings along one or moreshunting portions or members (e.g., to maintain shunting portions ormembers along an interior of a catheter or other medical instrument) canprovide several benefits and advantages to the resulting devices andsystems, as well as the resulting methods of use and treatment. Forexample, the coating(s) or layer(s) can: (i) improve the conductivecooling effects of the irrigation fluid (which, in turn, can permitirrigation flow rates and the resultant volume of fluid infused into thepatient to be significantly decreased; in some embodiments, lowerirrigation rates result in better temperature measurement accuracy, astemperature sensors are less likely to be flooded by the irrigationfluid), (ii) improve manufacturing and operational aspects of thecatheter or other medical instrument (e.g., can compensate for theeffects of the superficial layer of the heat shunt portions becomingelectrically conductive as a result of the cutting process, therebyproviding more flexibility to the manufacture of the heat shunt portionswhile still maintaining a consistent outer surface for the catheter orother medical instrument), (iii) provide additional protection againstthe formation of hot spots or localized heating at or near the proximalends of the proximal electrode during use and/or the like.

According to some embodiments, as discussed in greater detail herein,the primary heat shunting mechanism of catheters that include heatshunting networks occurs via the cooling action of (e.g., via conductiveheat transfer to) the irrigation fluid running within an interior of thecatheter or other medical instrument. In some embodiments, theconductive cooling capacity of room-temperature (e.g., around 27° C.)irrigation fluid flowing through the heat shunting network (e.g., thediamond or other heat shunting network that is in thermal contact withthe irrigation passage extending through the distal portion of thecatheter or other medical instrument) is greater than that of theconvective cooling provided by the blood flow over the external surfaceof the heat shunting network. This occurs, in part, because thetemperature of blood (e.g., which is around 37° C.) is notably higherthan the temperature of irrigation fluid. Also, this may occur, becausethe heat transport velocity of the blood may be inferior to thatprovided by the irrigation fluid (e.g. the blood flow velocity is low incertain regions of the heart, for example in parts of the atria or undervalve leaflets). Thus, by thermally insulating the external surfaces ofheat shunting portions or members (e.g., diamond), the conductivecooling effects of the irrigation fluid (e.g., via heat transfer to theirrigation fluid) can be augmented. In some embodiments, this can helpto significantly decrease the irrigation flow rates and the resultantvolume of fluid infused into the patient. Low irrigation flow rates canresult in improved temperature sensing accuracy, as the temperaturesensors associated with electrodes are less likely to be flooded by theirrigation fluid (e.g., the volume of required irrigation fluid isreduced).

In some embodiments, when industrial diamond or other heat shuntingmembers or portions are cut in preparation for incorporation into acatheter, the resulting superficial portion (e.g., outer surface orlayer, portions immediately adjacent (e.g., within 0.1 mm) the outersurface or layer, etc.) can become at least partially electricallyconductive (e.g., especially vis-à-vis the electrical properties of theuncut diamond or other heat shunting material). For example, in somearrangements, the electrical conductivity of industrial diamond or otherheat shunting material that is cut or otherwise prepared can increase by1% to 100% (e.g., 1-5, 5-10, 10-20, 20-50, 50-100, 25-75, 20-100%,values and ranges between the foregoing), or more that 100% (e.g.,100-150, 150-200, 200-300%, more than 300%, etc.), relative to uncut orotherwise undisturbed or unprepared material. As a result, in someembodiments, such a superficial portion (e.g., surface, layer or area)can present problems during operation of the catheter or other medicalinstrument into which it is incorporated if it is exposed to theexterior of the catheter or medical instrument. For example, theelectrical conductivity of the superficial portion (e.g., surface, layeror area) of diamond or other heat shunting material can cause electricalshort-circuiting of the two electrodes (or electrode portions) includedin the catheter or medical instrument. Accordingly, providing anelectrically non-conductive layer or coating along the exterior surfacesof certain heat shunting portions, as discussed herein, can provideoperational benefits to the manufacturing and performance of theresulting catheter or medical instrument. This, in turn, may result inout-of-speciation performance of system features such as tissue contactsensing, impedance measurements, energy delivery and/or the like. Thus,in some embodiments, all or the majority of the heat shunting members orportions included in a catheter or other medical instrument are notexposed to the exterior of the catheter or medical instrument. In someconfigurations, none of the diamond or other heat shunting network isexposed to the exterior of the catheter or other medical instrument. Inother embodiments, 70-100% (e.g., 70-75, 75-80, 80-85, 85-90, 90-95,95-100%, percentages between the foregoing ranges, etc.), 50-70%, orless than 50% of an outer surface area of the heat shunting is coveredor coated with a layer or coating.

As illustrated in FIG. 20, one or more thermally-insulating layers orcoatings 6070 can be placed around the exterior of the heat shuntportions 6050 that are exposed to the outside of the catheter or othermedical instrument 6000. The layer or coating 6070 can include one ormore thermally insulative materials (e.g., thermoset polymers,polyimide, PEEK, polyester, polyethylene, polyurethane, pebax, nylon,hydratable polymers, other polymers, etc.). In some embodiments, suchmaterials have a thermal conductivity of less than 0.001 W/cm*K (e.g.,0.0001-0.001, 0.001-0.0025, 0.0025-0.001 W/cm*K, less than 0.0001W/cm*K, etc.). The thickness of such a layer or coating 6070 can beabout 50 μm (2 mils) or less. For example, in some embodiments, thethickness of the layer or coating 6070 is 1-50 μm (e.g., 1-5, 5-10,10-20, 20-30, 30-40, 40-50 μm, values between the foregoing ranges,etc.) or less than 1 μm (e.g., 0.01-0.5, 0.5-0.75, 0.75-1 μm, valuesbetween the foregoing ranges, etc.). In other embodiments, however, thethickness of the layer or coating 6070 is greater than 50 μm, such as,for example, 50-100 (e.g., 50-55, 55-60, 60-65, 65-70, 70-75, 75-80,80-85, 85-90, 90-95, 95-100, values between the foregoing ranges),100-200 (e.g., 100-110, 110-120, 120-130, 130-140, 140-150, 150-160,160-170, 170-180, 180-190, 190-200, values between the foregoingranges), 200-300, 300-400, 400-500, 500-1000, 1000-5000 μm, greater than5000 μm.

In any embodiments where the heat shunting portions include a coating orlayer, such a coating or layer can be a single or unitary coating orlayer. However, in other embodiments, more than one layer or coating canbe positioned along the exterior of one or more heat shunting members orportions, as desired or required. For example, in some arrangements, thecoating or layer 6070 can include two or more (e.g., 2, 3, 4, 5, morethan 5) separate coatings or layers. Such separate coatings or layerscan be positioned along the catheter 6000 either individually or as asingle member, as desired or required by the particular technologiesused to secure such coatings or layers along the desired surfaces of theheat shunting members or portions.

The coating or layer 6070 can be positioned along the exterior of theheat shunt portions using a variety of technologies, such as, forexample, glues or other adhesives, press-fit methods, dip molding, othermolding technologies and/or the like. As noted above, depending on thespecific methods and/or technologies used, the coating or layer 6070 caninclude two or more separate coatings or layers, which may be positionedalong heat shunt members or portions separately or as a single coatingor layer, as desired or required. Further, the coating or layer 6070 canbe positioned along heat shunt members directly or indirectly. Forexample, in some embodiments, the coating or layer 6070 directlycontacts and is secured directly to an adjacent surface of a heat shuntmember or portion. However, in other embodiments, the coating or layer6070 does not contact or is not secured directly to an adjacent surfaceof a heat shunt member or portion. In such arrangements, for instance,one or more intermediate layers, coatings, structures (e.g., air gaps)or other members can be positioned between a heat shunt member orportion and the coating or layer 6070.

As noted herein, the various embodiments of a catheter or other medicalinstrument can include an irrigation channel that is responsible for themajority of heat transfer away from the electrode(s) or electrodeportion(s) positioned along a distal end of the catheter or medicalinstrument. In embodiments that comprise diamond and/or other heatshunting materials and/or configurations, heat can be transferred toirrigation fluid (e.g., flowing through an irrigation channel) via theheat shunting network. As discussed in greater detail herein, such aheat shunting network facilitates heat transfer away from the source(e.g., electrodes) without itself retaining heat or retaining verylittle heat. Relatedly, heat is transferred away from potential hotspots that form at the edges of electrodes and are shunted through theheat shunt network into the irrigation channel. From the irrigationchannel, via convective cooling, heat can be advantageously releasedinto the blood stream and dissipated. In closed irrigation systems, heatcan be removed from the system without expelling irrigation fluid intothe subject. The layer(s) and/or coating(s) discussed above can beincorporated into any catheter or other medical instrument device orsystem disclosed herein or equivalent thereof.

FIGS. 21A and 21B schematically illustrate a distal portion of anopen-irrigated ablation catheter 3420 in perpendicular contact andparallel contact, respectively, with tissue and formation of thermallesions by delivering energy to the tissue using the ablation catheter3420. In accordance with several embodiments, the ablation cathetershaving multiple temperature-measurement devices described hereinadvantageously facilitate determination of, among other things: anorientation of the distal tip of the ablation catheter with respect tothe tissue (e.g., electrode-tissue orientation), an estimated peaktemperature within the thermal lesion, and/or a location of the peaktemperature zone within the thermal lesion.

As mentioned above, the temperature-measurement devices 3425 may send ortransmit signals to at least one processing device (e.g., processor 46of FIG. 1). The processing device may be programmed to executeinstructions stored on one or more computer-readable storage media todetermine temperature measurements for each of thetemperature-measurement devices 3425 and to compare the determinedtemperature measurements with each other to determine an orientation ofthe distal tip of the ablation catheter with respect to the tissue(e.g., electrode-tissue orientation) based, at least in part, on thecomparisons. Additional details regarding the comparisons are providedbelow in connection with the discussion of FIGS. 23D-23F. The processingdevice may select (e.g., determine) an orientation from one of threeorientations (e.g., parallel, perpendicular, or angled (e.g., skewed oroblique) orientations).

For example, the differences in the spreads of the temperaturemeasurement profiles or values between the proximaltemperature-measurement devices and the distal temperature-measurementdevices may be used to determine orientation. As one example, if thetemperature measurements received from the distaltemperature-measurement devices are all greater (e.g., hotter) than thetemperature measurements received from the proximaltemperature-measurement devices, then the processor may determine thatthe orientation is perpendicular. If the temperature measurementsreceived from at least one proximal temperature-measurement device andat least one corresponding distal temperature-measurement device aresimilar, then the processor may determine that the orientation isparallel.

As other examples, for embodiments using three temperature-measurementdevices, if two of three proximal temperature-measurement devicesgenerate much lower (and generally equal) temperature measurements thanthe third proximal-temperature measurement device, then the processingdevice may determine that the orientation is parallel. For embodimentsusing three temperature-measurement devices, if the temperaturemeasurements received from a first proximal temperature-measurementdevice are appreciably greater than temperature measurements from asecond proximal temperature-measurement device and if the temperaturemeasurements received from the second proximal temperature-measurementdevice are appreciably greater than temperature measurements receivedfrom a third proximal temperature-measurement device, then theprocessing device may determine that the orientation is neither parallelnor perpendicular but skewed at an angle (e.g., oblique orientation).Additional details regarding orientation determination are providedbelow in connection with the discussion of FIGS. 23C-23E. In someembodiments, orientation may be confirmed using fluoroscopic imaging,ICE imaging or other imaging methods or techniques. Orientation may alsobe confirmed using a tissue mapping system, such as a three-dimensionalcardiac mapping system.

In some embodiments, the determined orientation may be output on adisplay (e.g., a graphical user interface) for visibility by a user(e.g., clinical professional). The output may comprise one or moregraphical images indicative of an orientation and/or alphanumericinformation indicative of the orientation (e.g., a letter, word, phraseor number). Additional details regarding output will be described inconnection with FIGS. 23F-1, 23F-2 and 23F-3. The processing device mayapply correction factors to the temperature measurements received fromthe temperature-measurement devices based on the determined orientationin order to generate more accurate estimates of a peak temperature ofthe thermal lesion. For example, if a perpendicular orientation isdetermined, then a correction factor or function corresponding to thedistal temperature-measurement devices may be applied to determine theestimated peak temperature.

The processing device may comprise a temperature acquisition module anda temperature processing module, in some embodiments. The temperatureacquisition module may be configured to receive as input temperaturesignals (e.g., analog signals) generated by each of thetemperature-measurement devices. The input signals may be continuouslyreceived at prescribed time periods or points in time. The temperatureacquisition module may be configured to covert analog signals intodigital signals. The temperature processing module may receive thedigital signals output from the temperature acquisition module and applycorrection factors or functions to them to estimate a hottest tissuetemperature, a peak temperature or a peak temperature in a thermallesion created in the vicinity of the electrode or other energy deliverymember(s). The temperature processing module may compute a compositetemperature from the temperature-measurement devices (e.g.,thermocouples) based on the following equation:

Tcomp(t)=k(t)*f(TC1(t),TC2(t), . . . ,TCn(t));

where Tcomp is the composite temperature, k is the k function orcorrection or adjustment function, f is a function of the thermocouplereadings TCi, i=1 to n. The k function may comprise a function over timeor a constant value. For example, a k function may be defined asfollows:

k(t)=e ^((−t/τ)) +k _(final)*(1−e ^((−t/τ)));

where τ is a time constant representative of the tissue time constantand k_(final) is a final value of k, as per a correction factor orfunction, such as described in connection with FIG. 22A below.

The temperature processing module may also be configured to determine anorientation of a distal tip of a medical instrument with respect totissue, as described above. The processing device may further comprisean output module and a feedback/monitoring module. The output module maybe configured to generate output for display on a display, such as thevarious outputs described herein. The feedback/monitoring modules may beconfigured to compare measured temperature values against apredetermined setpoint temperature or maximum temperature and toinitiate action (e.g., an alert to cause a user to adjust power or otherablation parameters or automatic reduction in power level or terminationof energy delivery (which may be temporary until the temperaturedecreases below the setpoint temperature). In various embodiments, thesetpoint, or maximum, temperature is between 50 and 90 degrees Celsius(e.g., 50, 55, 60, 65, 70, 75, 80, 85 degrees Celsius). In someembodiments, an algorithm identifies which temperature-measurementdevice (e.g., thermocouple) is currently recording the highesttemperature and selects that thermocouple to control the power deliveryrequired to reach and maintain the setpoint temperature or other targettemperature. As the tip electrode moves with respect to tissue anddifferent temperature-measurement devices come in greater or lessercontact with tissue, the processor or processing device mayautomatically select whichever temperature-measurement device is readingthe highest temperature to control the power delivery.

In accordance with several embodiments, there is a proportionalrelationship between the temperature gradient determined by thetemperature-measurement devices and the peak temperature of the lesion.From this relationship, a function or correction factor is generated orapplied based on numerical modeling (e.g., finite element methodmodeling techniques) and/or measurements stored in a look-up table toadjust or correct from the thermal gradient identified by thetemperature-measurement devices to determine the peak temperature. Thethermal gradient of an open-irrigated lesion is such that the lesionsurface is a little bit cooled and the peak temperature zone is deeper.The further the temperature-measurement devices can be buried intotissue, the better or more accurate the proportional relationship may bebetween the thermal gradient determined by the temperature-measurementdevices and the peak temperature. For example, the thermal gradient canbe estimated as:

ΔT/Δd=(T _(distal) −T _(proximal))/TC_separation distance

In other words, the temperature spatial gradient is estimated as thedifference in temperature between the distal and proximaltemperature-measurement devices divided by the distance between thedistal and proximal temperature-measurement devices. The peak tissuetemperature (where peak can be a hill or a valley) can then be estimatedas:

T _(peak) =ΔT/Δd*T _(peak) _(_) _(dist) +T _(distal)

The processing device may also determine an estimated location of thepeak temperature zone of the thermal lesion based, at least in part, onthe determined orientation and/or the temperature measurements. Forexample, for a perpendicular orientation, the peak temperature locationmay be determined to be horizontally centered in the thermal lesion. Insome embodiments, the processor may be configured to output informationindicative of the peak temperature location on a display (e.g., agraphical user interface). The information may include textualinformation and/or one or more graphical images.

FIG. 22A is a graph illustrating that temperature measurements obtainedfrom the temperature-measurement devices may be used to determine a peaktemperature by applying one or more analytical correction factors orfunctions to the temperature measurements (e.g., using numericalmodeling approximations or look-up tables). As shown in FIG. 22A, asingle correction factor or function (k) may be applied to each of thedistal temperature-measurement devices to determine the peaktemperature. In some embodiments, different correction factors orfunctions may be applied to each individual temperature-measurementdevice or to subsets of the groups of temperature-measurement devicesdepending on a determined orientation or on a comparison of thetemperature measurements obtained by the temperature-measurementdevices, thereby providing increased accuracy of peak temperature andpeak temperature zone location. The increased accuracy of peaktemperature and peak temperature zone location may advantageously resultin safer and more reliable ablation procedures because the ablationparameters may be adjusted based on feedback received by the processingunit from the temperature-measurement devices. In accordance withseveral embodiments, peak temperatures at a depth beneath the tissuesurface are accurately estimated without requiring microwave radiometry.With reference to FIG. 22A, the peak tissue temperature can be estimatedas follows:

T _(peak)(t)=e ^((−t/τ)) +k*(1−e ^((−t/τ)))*max(TCi(t));

where i spans the range of temperature-measurement devices, withmax(TCi(t)) representing the maximum temperature reading of thetemperature-measurement devices at time t. For example, FIG. 22B showsan implementation of the above formula. Trace 1 shows the estimated peaktissue temperature (T_(peak)) at a constant k value of 1.8 and a t valueof 1, whereas Traces 2, 3 and 4 show the actual tissue temperaturesmeasured at 1 mm, 3 mm and 5 mm, respectively, from the tissue surfaceusing tissue-embedded infrared probes. As seen, the estimated peaktissue temperature (T_(peak)) of Trace 1 tracks well the actual peaktissue temperature measured at 1 mm depth (Trace 2).

In another embodiment, a predictive model-based approach utilizing thebioheat equation may be utilized to estimate peak tissue temperature. Arecursive algorithm for determining the temperature T at a time point n,at a single point in a volume during treatment (e.g., RF ablation) maybe defined as follows:

$T_{n} = \frac{{\frac{\rho \cdot C}{dt} \cdot T_{n - 1}} + {W_{e} \cdot C \cdot T_{a}} + {P \cdot N}}{\frac{\rho \cdot C}{dt} + {W_{e} \cdot C}}$

where T_(n) is the current temperature, T_(n-1) is the previoustemperature, t is time, p is the tissue density, C is the specific heatof tissue, T_(a) is the core arterial temperature, W_(e) is an effectiveperfusion rate, and P·N provides an estimate of the volumetric powerdeposited in tissue. The above equation can be formulated at variousspatial locations, including the temperature-measurement devicelocation(s) as well as the location of peak temperature (e.g., hotspot). By utilizing this model at different locations, along withcalibration to determine the model parameters, mapping techniques can beutilized to predict the temperature at one spatial location usingmeasurement data from the other spatial location.

In some embodiments, the processing device is configured to output thepeak temperature or other output indicative of the peak temperature on adisplay (e.g., a graphical user interface). The output may comprisealphanumeric information (e.g., the temperature in degrees), one or moregraphical images, and/or a color indication. In some embodiments, theprocessor may generate an output configured to terminate energy deliveryif the determined peak temperature is above a threshold or maximumtemperature. The output may comprise a signal configured to causeautomatic termination of energy delivery or may comprise an alert(audible and/or visual) to cause a user to manually terminate energydelivery.

In various embodiments, ablation parameters may be adjusted based ontemperature measurements received from the temperature-measurementdevices. The ablation parameters may comprise, among other things,duration of ablation, power modulation, contact force, target orsetpoint temperature, a maximum temperature. For example, the processor46 (FIG. 1) may be configured to send control signals to the energydelivery module 40 based on the temperature measurements (and othermeasurements or estimations derived or otherwise determined therefrom)received from the plurality of distributed temperature-measurementdevices.

In one embodiment, the energy delivery module 40 (FIG. 1) may be set torun in a temperature control mode, wherein radiofrequency energy of acertain power level is delivered and a maximum temperature is identifiedwhich cannot be exceeded. Each of the temperature-measurement devicesmay be monitored (either simultaneously or via toggled queries) on aperiodic or continuous basis. If the maximum temperature is reached orexceeded, as determined by temperature measurements received from any ofthe temperature-measurement devices of the ablation catheters describedherein, control signals may be sent to the energy delivery module toadjust ablation parameters (e.g., reduction in power level) to reducethe temperature or to terminate energy delivery (temporarily orotherwise) until the temperature is reduced below the maximumtemperature. The adjustments may be effected for example by aproportional-integral-derivative controller (PID controller) of theenergy delivery module 40. In another embodiment, the energy deliverymodule 40 may be set to run in a power control mode, in which a certainlevel of power is applied continuously and the temperature measurementsreceived from each of the temperature-measurement devices are monitoredto make sure a maximum temperature is not exceeded. In some embodiments,a temperature-controlled mode comprises specifying a setpointtemperature (e.g., 70 degrees Celsius, 75 degrees Celsius, 80 degreesCelsius, and then adjusting power or other parameters to maintaintemperature at, below or near the setpoint temperature, as determinedfrom the temperature measurements received from each of thetemperature-measurement devices. As the tip electrode moves with respectto tissue and different temperature-measurement devices come in greateror lesser contact with tissue, a processor or processing device of theenergy delivery module may automatically select whichevertemperature-measurement device is reading the highest temperature tocontrol the power delivery.

Table 1 below shows examples of ablation parameters used in various testablation procedures using an embodiment of an ablation catheterdescribed herein.

TABLE 1 Blood Max Tissue flow Irrigation Power Temp Lesion LesionImpedance Orientation (cm/s) (ml/min) (W) (° C.) width (mm) depth (mm)(Ohms) Parallel 0.5 15 13.3 91.7 9.8 5.2 85 Parallel 25 15 15.8 94.9 9.25.4 85 Parallel 0.5 0 8.6 98.8 11.2 4.7 85 Parallel 25 0 14.9 94.8 10.05.3 85 Perpend. 0.5 15 16.8 99.4 11 5.6 83 Perpend. 25 15 18.1 99.9 10.35.8 83 Perpend. 0.5 0 10.4 97.9 10.3 4.8 83 Perpend. 25 0 16.9 95.7 9.35.3 83

As can be seen from the data in Table 1, the maximum tissue temperatureand lesion sizes remained relatively constant with or without irrigationand/or with or without significant blood flow by modulating the power.The multi-variant or multiple temperature-measurement device systemaccording to embodiments of this invention ensures appropriate tissueablation under different electrode-tissue orientations. As explainedabove, the electrode-tissue orientation can be determined based onreadings from the multiple distributed temperature-measurement devices.If both proximal and distal temperatures become dominant, then theelectrode orientation may be estimated or indicated to be parallel totissue. Similarly, when the distal temperatures are dominant, then theelectrode orientation may be inferred, estimated and/or indicated to beperpendicular to tissue. Combinations of proximal and distal dominanttemperatures may provide indications for oblique electrode orientations.FIG. 23A illustrates a plot of temperature data from the multipletemperature-measurement devices (e.g., thermocouples) that areindicative of a perpendicular orientation and FIG. 23B illustrates aplot of temperature data from the multiple temperature-measurementdevices (e.g., thermocouples) that are indicative of an obliqueorientation.

In accordance with several embodiments, a treatment system comprises amedical instrument (e.g., an ablation catheter), at least one processor,and an energy source (e.g., an ablation source such as a radiofrequencygenerator). The medical instrument comprises or consists essentially ofan elongate body having a proximal end and a distal end, an energydelivery member (e.g., a high-resolution combination electrode assemblycomprised of a proximal electrode portion and a distal electrode portionspaced apart from the proximal electrode portion) positioned along thedistal end of the elongate body, and a plurality of distributedtemperature-measurement devices (e.g., thermocouples or othertemperature sensors) carried by or positioned along or within theelongate body or a portion of the energy delivery member. In someembodiments, the distributed temperature-measurement devices comprise adistal plurality of temperature-measurement devices positioned at thedistal end of the elongate body (e.g., along a distal surface of theenergy delivery member) and a proximal plurality oftemperature-measurement devices positioned along the elongate body andspaced apart proximally of the distal plurality oftemperature-measurement devices, as described and illustrated inconnection with certain embodiments of the ablation catheters herein. Inone embodiment, the proximal plurality of temperature-measurementdevices consists of three co-planar temperature-measurement devicesspaced equally apart around a circumference of the elongate body and thedistal plurality of temperature-measurement devices consists of threeco-planar temperature-measurement devices spaced apart symmetrically orequally around a central longitudinal axis extending through the distalend of the elongate body. The energy delivery member may be configuredto contact tissue of a subject and to deliver energy generated by theenergy source to the tissue. In some embodiments, the energy issufficient to at least partially ablate the tissue. The energy source ofthe embodiment of the system may be configured to provide the energy tothe energy delivery member through one or more conductors (e.g., wires,cables, etc.) extending from the energy source to the energy deliverymember. In several embodiments, the energy is radiofrequency energy.

The at least one processor of the embodiment of the treatment system(e.g., ablation system) may be programmed or otherwise configured (e.g.,by execution of instructions stored on a non-transitorycomputer-readable storage medium) to receive signals from each of thetemperature-measurement devices indicative of temperature and determinean orientation, or alignment, of the distal end of the elongate body(e.g., electrode-tissue orientation) of the ablation catheter withrespect to the tissue (e.g., orientation, or alignment, of the outerdistal surface of the electrode or other energy delivery member with atarget surface) based on the received signals. In accordance withseveral embodiments, multiple separate processing devices are used inparallel to simultaneously perform portions of the processes describedherein so as to increase processing speeds. Each of the separateprocessing devices may be controlled by a main processing device orcontrol unit that receives output from each of the separate processingdevices.

In accordance with several embodiments, determination of orientation atneighboring treatment sites facilitates increased likelihood orconfirmation of treatment efficacy (e.g., continuous lesion formationwithout gaps). For example, if it is determined that the ablationcatheter was in a perpendicular orientation at two adjacent ablationsites, there may be an increased probability that the lesion profiles donot overlap and the clinical professional may decide to perform anotherablation between the two adjacent ablation sites to increase thelikelihood of continuous lesion formation without gaps. In accordancewith several embodiments, determination of orientation is performedduring delivery of energy (e.g., radiofrequency energy). In instanceswhere determination of orientation is performed during energy delivery,it can be particularly advantageous to determine orientation early on inthe energy delivery process (e.g., within a few seconds after initiationof energy delivery) so as to provide increased confidence that aparticular lesion profile or pattern (e.g., volume, shape or zone) wasformed by the energy delivery. For example, parallel orientations mayform shallower but longer or wider lesion profiles, perpendicularorientations may form deeper but narrower lesion profiles and obliqueorientations may form lesion profiles somewhere in between the paralleland perpendicular orientations. In some embodiments, a particularorientation may be targeted by a clinical professional and theorientation determination can confirm to the clinical professional thatthe targeted orientation has been achieved. In some instances, aclinical professional may decide to terminate energy delivery if thetargeted orientation is not achieved, to adjust parameters of the energydelivery based on the determined orientation, or to perform anadditional treatment at a treatment site close to the current treatmentsite to increase the likelihood of continuous lesion formation withoutgaps.

FIG. 23C illustrates an embodiment of a process 23000 for determiningorientation of a distal end of a medical instrument (e.g., ablationcatheter) with respect to target tissue (e.g., vessel surface or cardiactissue surface) while energy (e.g., radiofrequency energy) is beingapplied to the target tissue by the medical instrument. The process23000 may be executed by one or more processors communicatively coupledwith the medical instrument (e.g., via wires or cables or via wirelesscommunication such as via Bluetooth or a wireless network) uponexecution of instructions stored on one or more computer-readable media(e.g., non-transitory, non-volatile memory or storage devices). Theprocess 23000 may advantageously result in orientation, or alignment,determination in a very short amount of time following initiation oftreatment (e.g., within less than fifteen seconds, within less than tenseconds, within less than eight seconds, within less than five seconds,within less than three seconds, within less than two seconds followinginitiation of energy delivery, in the first 40% of total treatmentduration, in the first 30% of total treatment duration, in the first 25%of total treatment duration, in the first 20% of total treatmentduration, in the first 15% of total treatment duration, in the first 10%of total treatment duration, in the first 5% of total treatmentduration). Treatment times (e.g., ablation durations) may be very short(e.g., less than 30 seconds); accordingly, if orientation determinationis not made quickly, the orientation determination may not be performeduntil the treatment is either over or substantially complete and thedetermined orientation at that time may not accurately reflect theorientation during the majority of the treatment because the orientationof the ablation catheter or other medical instrument may change duringthe treatment (e.g., due to movement of tissue caused by contraction andrelaxation of muscle tissue, patient or operator movement, and/orrespiration).

The process 23000 begins upon initiation of treatment (e.g., ablativeenergy delivery) and includes three phases: an initial phase, atemperature rise phase, and a steady state phase. In the initial phase,the at least one processor obtains temperature measurements from aplurality of temperature-measurement devices distributed along thelength of an elongate body of the medical instrument for a first timeperiod (Block 23005). Obtaining the temperature measurements maycomprise receiving signals indicative of temperature and determiningtemperature measurement values based on the received signals (which maybe performed, for example, by a temperature processing module executedby the at least one processor, such as described above). The first timeperiod can start upon initiation of treatment (e.g., energy delivery) bythe medical instrument and may continue for a first time duration (e.g.,between 1 and 5 seconds, between 1 and 2 seconds, between 1 and 3seconds, between 2 and 4 seconds, between 3 and 5 seconds, 1 second, 1.5seconds, 2 seconds, 2.5 seconds, 3 seconds, 3.5 seconds, 4 seconds, 4.5seconds, 5 seconds, overlapping ranges thereof or any value within theranges). In some embodiments, the temperature measurements are obtainedat a plurality of time points, or measurement points (e.g., at regularintervals within the first time duration of the initial phase or atmultiple irregular intervals or non-periodic points of time within thefirst time duration of the initial phase). The first time duration maybe varied as desired and/or required for optimization. Measurements canbe obtained and recorded at any desired frequency (e.g., every 1 ms,every 5 ms, every 10 ms, every 50 ms, or every 100 ms). At Block 23010,a starting temperature is determined for each temperature-measurementdevice (e.g., thermocouple or thermistor) based on the temperaturemeasurements obtained during the first time period. Eachtemperature-measurement device may be associated with a channel that canbe tracked and plotted (and output on a display for viewing). In someembodiments, the starting temperature is determined by averaging thetemperature measurements obtained during the first time period. Any ofthe configurations or arrangements of the temperature-measurementdevices described herein may be used. For example, thetemperature-measurement devices may include a distal plurality oftemperature-measurement devices and a proximal plurality oftemperature-measurement devices spaced proximal to the distal pluralityof temperature-measurement devices as discussed herein.

After determining a starting temperature, the process 23000 proceeds tothe temperature rise phase. The temperature rise phase corresponds tothe time during which the temperature measurements are increasing as aresult of tissue heating caused by the application of energy (e.g., RFenergy) to the tissue. In the temperature rise phase, temperaturemeasurements are continuously obtained from each of thetemperature-measurement devices and recorded (Block 23015). Obtainingthe temperature measurements may comprise receiving signals indicativeof temperature and determining temperature measurement values based onthe received signals. Again, the frequency of the temperaturemeasurements may vary as desired and/or required for optimization. Insome embodiments, the temperature measurements are obtained at aplurality of time points, or measurement points (e.g., at regularintervals within a time period of the temperature rise phase or atmultiple irregular intervals or non-periodic points of time within thetime period of the temperature rise phase). For example, temperaturemeasurements may be obtained every 0.1 seconds, every 0.5 seconds, everysecond, etc. The temperature rise phase may continue for a second timeperiod (e.g., from one second to thirty seconds after initiation ofenergy delivery, from one second to twenty seconds after initiation ofenergy delivery, from one second to eighteen seconds after initiation ofenergy delivery, from five seconds to eighteen seconds after initiationof energy delivery, from three seconds to thirteen seconds afterinitiation of energy delivery, from five seconds to ten seconds afterinitiation of energy delivery, overlapping ranges thereof or any valuewithin the ranges).

At every measurement point in time during the temperature rise phase, acharacteristic of a temperature response is determined (e.g., computedor calculated by the at least one processor or computing device) foreach temperature-measurement device (or each channel associated with arespective temperature-measurement device) based on the obtainedtemperature measurements (Block 23020). In some embodiments, thecharacteristic is a rate of change of temperature (e.g., how fasttemperature measurement values obtained by the temperature-measurementdevices increase over time). As another example, the characteristic maybe a temperature rise value that is computed for eachtemperature-measurement device (or each channel associated with arespective temperature-measurement device) by subtracting the startingtemperature value from a current temperature value (for example, Tn−Ts).In some embodiments, a moving average is applied over time to remove“noise” or fluctuations in temperature measurement values and thestarting temperature value is subtracted from the moving average todetermine the temperature rise value. The moving average window maynominally be 1 second, but may be varied to address variation in thetemperature-measurement response such as cardiac and respiratoryartifacts (e.g., 0.1 seconds, 0.5 seconds, 1 second, 1.5 seconds, 2seconds, 2.5 seconds, 3 seconds, 3.5 seconds, 4 seconds, 4.5 seconds, 5seconds, or any value between 0.1 seconds and 5 seconds). A rate ofchange may be determined by dividing the temperature rise value by thetime duration between the current time and the start time. For example,at second n there is a measured temperature value Tn between second n−1and second n. The starting temperature value may be subtracted from Tnand then divided by n to get the rate of change at second n.

At Block 23025, the one or more processing devices (e.g., upon executionof a temperature processing module) determine an orientation, oralignment, of the distal end of the medical instrument based on one ormore orientation criteria (e.g., thresholds, tests or conditions) thatrely on the determined characteristic for at least two of thetemperature-measurement devices. The orientation determination may beperformed at each measurement point, or point in time in which ameasurement is obtained or determined, thereby advantageously indicatingif the orientation changes during the treatment procedure (e.g., as aresult of patient or operator movement or other perturbations). Thedetermination of the orientation may include performing differentcomparisons between the characteristics of the temperature responses(e.g., temperature rise values or rates of change) between two or moreof the temperature-measurement devices. For example, comparisons may beperformed at each of the time points, or measurement points, between thecharacteristics of the proximal temperature-measurement devices and thedistal temperature-measurement devices (such as average of thetemperature rise values or rates of change of the proximaltemperature-measurement devices compared with the average of thetemperature rise values or rates of change of the distaltemperature-measurement devices, or the minimum of the temperature risevalues or rates of change of the distal temperature-measurement devicescompared with the maximum of the temperature rise values or rates ofchange of the proximal temperature-measurement devices, or the maximumof the temperature rise values or rates of change of the distaltemperature-measurement devices compared with the minimum of thetemperature rise values or rates of change of the proximaltemperature-measurement devices). As one example, if the averageproximal temperature rise or rate of change is greater than the averagedistal temperature rise or rate of change by a certain factor N, where Ncan be any real number, the one or more processing devices may determinethat the orientation is oblique. In accordance with several embodiments,by determining orientation based on comparisons of characteristics of atemperature response (e.g. rate of change or rise value or rise timecomparisons) instead of on comparisons of temperature measurement valuesthemselves or the spread of the temperature-measurement values once theyhave reached a steady state, accurate determinations of orientation canbe made much more quickly after initiation of energy delivery.

The orientation criteria may be determined based on empirical data andmay be stored in a look-up table or in memory. In some embodiments, theorientation criteria include time-dependent thresholds in addition to orinstead of static thresholds or conditions. For example, the maximumproximal temperature rise or rate of change can be subtracted from theminimum distal temperature rise or rate of change and this value can becompared to a time-dependent threshold as follows:DRmin−PRmax<=A*(t−B)+C, where DRmin is the smallest temperature risevalue of the distal temperature-measurement devices and PRmax is thelargest temperature rise value of the proximal temperature-measurementdevices and A, B and C are constants determined by empirical data anddefine how the threshold changes as a function of time. The orientationcriteria for a respective orientation option may include multiplecriteria of which one, some or all must be satisfied for thatorientation option to be selected. Multiple criteria may be used toaccount for different alignments or orientations caused by anatomicalvariations in the temperature rise phase. For example, for an obliqueorientation it may be possible in one instance that a distal electrodemember (or one or more temperature-measurement devices along the distalelectrode member) of the electrode is in contact with tissue while aproximal electrode member (or one or more temperature-measurementdevices spaced proximal to the distal electrode member) is not incontact with tissue whereas in another instance the distal electrodemember (or one or more temperature-measurement devices along the distalelectrode member) is not in contact with tissue while a proximalelectrode member (or one or more temperature-measurement devices spacedproximal to the distal electrode member) is in contact with tissue. Bothof these instances (which may be caused by anatomical variations) mayhave quite different temperature response characteristics but shouldboth be determined to be oblique orientations in accordance with severalembodiments. In addition, in a parallel orientation, it is possible thatonly one proximal temperature-measurement device is in contact withtissue (and therefore generating higher temperature measurements) whiletwo distal temperature-measurement devices are in contact with tissue(and therefore generating higher temperature measurements). If onlyaverage value comparisons are made, an improper orientation may bedetermined by the at least one processing device. Accordingly, differentorientation criteria may be needed to account for the variance inpossible orientations (and accordingly variance in temperature responsecharacteristics) for a single orientation option.

The orientation may be determined from one of two possible orientationoptions (e.g., parallel or perpendicular) or one of three orientationoptions (e.g., oblique, parallel or perpendicular). The definition ofoblique, parallel and perpendicular may be adjusted as desired and/orrequired for usability and/or performance factors. In accordance withseveral embodiments involving three orientation options, a parallelorientation may be considered to be from 0 to 20 degrees (or 160 to 180degrees), an oblique orientation may be considered to be from 20 degreesto 80 degrees (or 120 to 160 degrees) and a perpendicular orientationmay be considered to be from 80 to 120 degrees (assuming a 0 or 180degree rotation (between the medical instrument and tissue) to beperfectly parallel and a 90 degree rotation to be perfectlyperpendicular). In embodiments involving three orientation options, thedetermination of orientation proceeds with first determining whether oneor more orientation criteria of a first orientation are satisfied. Ifthe one or more orientation criteria for the first orientation aresatisfied, the one or more processing devices optionally generate anoutput indicative of the first orientation at Block 23030. If the one ormore orientation criteria of the first orientation are not met, then theone or more processing devices determine whether one or more orientationcriteria of a second orientation are met. If the one or more orientationcriteria for the second orientation are satisfied, the one or moreprocessing devices optionally generate an output indicative of thesecond orientation at Block 23030. If the one or more orientationcriteria of the second orientation are not met, then the one or moreprocessing devices determining that the orientation must be the thirdorientation by default since there are only three orientation optionsand the one or more processing devices optionally generate an outputindicative of the third orientation at Block 23030. If only twoorientation options are available, if the criteria associated with thefirst orientation are not satisfied, then the second orientation isselected by default. The orientation criteria may vary depending on theorder in which the orientation options are tested. If multiple criteriaare associated with a particular orientation being tested, the tests maybe performed in parallel by separate processors to speed up theorientation determination process 23000.

As one example, the process 23000 may first test for an obliqueorientation in the temperature rise phase. The oblique orientationcriteria may include tests that involve comparing the averagetemperature rise or rate of temperature change of distaltemperature-measurement devices and the proximal temperature devices(e.g., that the proximal average temperature rise or rate of temperaturechange is greater than or equal to the distal average temperature riseor rate of temperature change by a predetermined factor) and/orcomparing the minimum temperature rise or rate of temperature change ofthe distal temperature-measurement devices with the maximum temperaturerise or rate of temperature change of the proximaltemperature-measurement devices (e.g., that the difference is less thanor equal to a predetermined amount, which may be determined using atime-dependent equation, such as A*(t−B)+C, where A, B and C areconstants and t is time in seconds). If the oblique orientation criteria(which may be one criterion or a combination of multiple criteria) aresatisfied, then an oblique orientation is determined. Otherwise, theprocess 23000 may proceed to test for a parallel orientation. Theparallel orientation criteria may include tests that involve comparingthe average temperature rise or rate of temperature change of distaltemperature-measurement devices and the proximal temperature devices(e.g., that the absolute value of the difference between the twoaverages divided by the proximal average temperature rise or rate oftemperature change is less than or equal to a predetermined amount)and/or comparing a maximum temperature rise or rate of temperaturechange of the distal and proximal temperature-measurement devices (e.g.,that the difference between the maximum values is less than or equal toa predetermined amount, which may be determined using a time-dependentequation, such as A*(t−B)+C, where A, B and C are constants and t istime in seconds). If the parallel orientation criteria (which may be onecriterion or a combination of multiple criteria) are satisfied, then aparallel orientation is determined. Otherwise, the process 23000 maydetermine that the orientation is perpendicular.

After the second period of time has elapsed, the process 23000 proceedsto a steady state phase, corresponding to a third time period in whichthe temperature measurement values (or the profiles of the channelsplotted on a graph) have reached a steady state such that thetemperature measurement values (e.g., peak temperature measurementvalues) do not change or fluctuate by a significant amount (e.g., lessthan 20%, less than 15%, less than 10%, less than 5%, less than 4%, lessthan 3%, less than 2%) between measurement points, or points in time inwhich measurement values are obtained. In accordance with severalembodiments, because the temperature measurement values are not normallychanging significantly in the steady state phase, orientation, oralignment, determinations do not need to be made based on time-dependentconditions or on characteristics of temperature response such as rate ofchange or temperature rise values. Accordingly, in the steady statephase, the orientation determinations are made using a different set oforientation criteria than the orientation criteria used in thetemperature rise phase. While the temperature measurement values arenominally not changing significantly, the orientation determinations inthe steady state phase may be designed to react to deviations andchanges in temperature due to, for example, patient or operator movementor other perturbations. Again, the orientation criteria for the steadystate phase are different for each orientation option and may varydepending on the order in which the orientation options are tested.

At Block 23035, temperature measurements (e.g., values) are continuouslyobtained at periodic intervals (e.g., plurality of time points, ormeasurement points) from each of the distributed temperature-measurementdevices during the third time period. Similar to the temperature risephase, a moving average may be applied to each of thetemperature-measurement device channels; however, the averaging windowmay be different for the steady-state phase as a result of the deviationor fluctuation in temperature measurement values being low in thesteady-state phase. For example, the averaging window may be longer inthe steady-state phase than in the temperature rise phase. The averagingwindow may nominally be 5 seconds, but may be varied depending on thetype of instrument utilized and the therapy being provided (e.g., anyvalue between 0.5 and 10 seconds, such as 0.5 seconds, 1 second, 1.5seconds, 2 seconds, 2.5 seconds, 3 seconds, 3.5 seconds, 4 seconds, 4.5seconds, 5 seconds, 5.5 seconds, 6 seconds, 6.5 seconds, 7 seconds, 7.5seconds, 8 seconds, 8.5 seconds, 9 seconds, 9.5 seconds, 10 seconds).Orientation of the distal end of the medical instrument (e.g., electrodetissue orientation) is continuously determined at each measurement pointduring the third time period based on the steady-state phase orientationcriteria, which are different than the temperature rise phaseorientation criteria (Block 23040). By continuously determiningorientation at each time measurement point, a more accurate estimationof the lesion profile formed by the treatment at that particular targetsite may be obtained and further treatment may be adjusted accordingly,if desired or required. In accordance with several embodiments, theorientation criteria in the steady state phase only comprise staticthresholds or conditions and not time-dependent thresholds orconditions. For example, the orientation criteria may compare one ormore of: a maximum of the temperature values of the distaltemperature-measurement devices or channels with the maximum of thetemperature values of the proximal temperature-measurement devices orchannels, a minimum of the temperature values of the distaltemperature-measurement-devices or channels with the maximum of thetemperature values of the proximal temperature-measurement devices orchannels or a maximum of the temperature values of the distaltemperature-measurement devices or channels with the minimum of thedistal temperature values of the proximal temperature-measurementdevices or channels.

The orientation criteria for the steady state phase may be based onempirical data and stored in a look-up table or memory. The orientationcriteria for a respective orientation option in the steady state phasemay include multiple criteria of which one, some or all must besatisfied for that orientation option to be selected. As for thetemperature rise phase, multiple criteria may be used to account fordifferent alignments or orientations caused by anatomical variations inthe steady state phase. For example, for an oblique orientation it maybe possible in one instance that a distal electrode member (or one ormore temperature-measurement devices along the distal electrode member)of the electrode is in contact with tissue while a proximal electrodemember (or one or more temperature-measurement devices spaced proximalto the distal electrode member) is not in contact with tissue whereas inanother instance the distal electrode member (or one or moretemperature-measurement devices along the distal electrode member) isnot in contact with tissue while a proximal electrode member (or one ormore temperature-measurement devices spaced proximal to the distalelectrode member) is in contact with tissue. Both of these instances(which may be caused by anatomical variations) may have quite differenttemperature-measurement values or temperature response characteristicsbut should both be determined to be oblique orientations in the steadystate phase in accordance with several embodiments. Accordingly,different orientation criteria may be needed to account for the variancein possible orientations (and accordingly variance in temperaturemeasurement values or temperature response characteristics) for a singleorientation option.

Similar to the temperature rise phase, the determination of orientationin the steady state phase can proceed with first determining whetherorientation criteria of a first orientation are met. If the criteria forthe first orientation are not met, then the process proceeds withdetermining whether criteria of a second orientation are met. If thecriteria are not met for the second orientation, then the process maydetermine that the orientation is the third orientation. At Block 23045,the one or more processing devices optionally generate an outputindicative of the determined orientation. The steady state phasecontinues until the application of energy is terminated. In otherembodiments, the temperature measurements obtained in the steady statephase may not be obtained at periodic intervals. In some embodiments,the process 23000 does not include the steady state phase and theprocess 23000 ends before Block 23035.

As one example of an orientation determination operation at Block 23040,the first orientation to be tested in the steady state phase is theoblique orientation. The oblique orientation may include one or more ofthe following: comparing the average temperature measurement values ofthe distal temperature-measurement devices and the proximal temperaturedevices (e.g., that the difference is less than a predetermined amount),comparing the maximum distal temperature measurement value and themaximum proximal temperature measurement value (e.g., the difference isless than a predetermined amount), comparing the minimum temperaturemeasurement value of the distal temperature-measurement devices and themaximum temperature measurement value of the proximal temperaturedevices, comparing the middle temperature measurement value of thedistal temperature-measurement devices and the maximum temperaturemeasurement value of the proximal temperature devices, comparing theminimum temperature measurement value of the proximaltemperature-measurement devices and the maximum temperature measurementvalue of the distal temperature devices, and comparing the middle (ormedian) temperature measurement value of the proximaltemperature-measurement devices and the maximum temperature measurementvalue of the distal temperature devices. One, some or all of thecriterial may need to be satisfied to have the oblique orientation bedetermined as the current orientation. If the oblique orientationcriteria (which may be one criterion or a combination of multiplecriteria) are satisfied, then an oblique orientation is determined.Otherwise, the process 23000 may proceed to test for a parallelorientation. The parallel orientation criteria may include tests thatinvolve comparing the average temperature measurement value of thedistal temperature-measurement devices and the proximal temperaturedevices (e.g., that the difference between the two averages is within apredetermined range) and/or comparing a maximum temperature measurementvalue of the distal and proximal temperature-measurement devices (e.g.,that the difference between the maximum values is within a predeterminedrange). If the parallel orientation criteria (which may be one criterionor a combination of multiple criteria) are satisfied, then a parallelorientation is determined. Otherwise, the process 23000 may determinethat the orientation is perpendicular.

Another example of an orientation determination operation at Block23040, the process 23000 may first test for a perpendicular orientationin the steady state phase. The perpendicular orientation criteria mayinclude tests that involve any one or more of the following: comparingthe maximum temperature measurement values of the distaltemperature-measurement devices and the proximal temperature devices(e.g., that the maximum distal temperature measurement value is greaterthan the maximum proximal temperature measurement value by apredetermined temperature value), comparing the minimum temperaturemeasurement value of the distal temperature-measurement devices with themaximum temperature measurement value of the proximaltemperature-measurement devices (e.g., that the difference is greaterthan a predetermined temperature value), comparing the maximum andmedian temperature values of the distal temperature-measurement deviceswith the maximum and minimum temperature measurement values of thedistal temperature-measurement devices (e.g., determining that thedifference between the maximum and middle temperature measurement valuesof the distal temperature-measurement devices is less than thedifference between the maximum and minimum temperature measurementvalues of the distal temperature-measurement devices by a predeterminedamount), or comparing the maximum and minimum temperature measurementvalues of the distal temperature-measurement devices with the maximumtemperature measurement values of the distal and proximaltemperature-measurement devices (e.g., that the difference between themaximum and minimum temperature measurement values of the distaltemperature-measurement devices is less than the difference between themaximum temperature measurement values of the distal and proximaltemperature-measurement devices). If the perpendicular orientationcriteria (which may be one criterion or a combination of multiplecriteria) are satisfied, then a perpendicular orientation is determined.Otherwise, the process 23000 may proceed to test for a parallelorientation. The parallel orientation criteria may include tests thatinvolve determining whether the difference between the maximumtemperature measurement values of the distal and proximaltemperature-measurement devices is within a predetermined range and/orwhether the difference between the average measurement values of thedistal and proximal temperature-measurement devices is within apredetermined range. If the parallel orientation criteria (which may beone criterion or a combination of multiple criteria) are satisfied, thena parallel orientation is determined. Otherwise, the process 23000 maydetermine that the orientation is oblique.

FIGS. 23D and 23E illustrate two example embodiments of processes 23050,23075 for determining an orientation of a distal end of a medicalinstrument with respect to a target region (e.g., cardiac tissue or avessel wall). Each of the processes 23050, 23075 starts with determiningor specifying orientation criteria (e.g., thresholds or conditions forat least two of the orientation options (Blocks 23055, 23080). Asdiscussed previously, the orientation criteria may include static and/ortime dependent thresholds or conditions. The orientation criteria mayhave been stored in memory or a look-up table prior to initiation of theprocess and simply accessed or may be determined in real-time. Theprocesses 23050, 23075 may be performed in either the temperature risephase or the steady state phase.

Process 23050 starts with determining whether one or more orientationcriteria for the oblique orientation are satisfied. The criteria mayinclude one criterion or multiple criteria. If multiple criteria, eitherone or all of the criteria may need to be satisfied. If the criteria forthe oblique orientation are satisfied, then an output indicative of anoblique orientation is generated at Block 23060. If the criteria for theoblique orientation are not satisfied, then the process 23050 proceedsto determine whether one or more orientation criteria for the parallelorientation are satisfied. If the criteria for the parallel orientationare satisfied, then an output indicative of a parallel orientation isgenerated at Block 23065. If the criteria for the parallel orientationare not satisfied, then an output indicative of a perpendicularorientation is generated at Block 23070 by default. The process 23075 issimilar to process 23050 except that the order of orientations ischanged such that a test is first performed for the perpendicularorientation (with an output being generated at Block 23085 indicative ofa perpendicular orientation if the respective orientation criteria aresatisfied) instead of for the oblique orientation and the defaultorientation is the oblique orientation instead of the perpendicularorientation (with an output being generated at Block 23095 indicative ofan oblique orientation if the orientation criteria for the perpendicularand parallel orientations are not satisfied). As with process 23050, anoutput indicative of a parallel orientation is generated at Block 23090if the orientation criteria for a parallel orientation are satisfied.The orientations may be tested in any order. For example, a parallelorientation may be tested for first instead of an oblique orientation orperpendicular orientation as shown in FIGS. 23D and 23E, respectively.In accordance with several embodiments, an oblique orientation is testedfirst because it is the most likely orientation and therefore testingfor the oblique orientation first may reduce determination time.

In some embodiments, the processor is configured to cause the outputindicative of a particular orientation that is generated by theprocesses 23050 and 23075 to a display. The output may comprise textualinformation (such as a word, phrase, letter or number). In someembodiments, the display comprises a graphical user interface and theoutput comprises one or more graphical images indicative of thedetermined orientation. The orientation determination processes areperformed at each time point or measurement point and the output iscontinuously updated based on the current orientation determination,thereby advantageously indicating if an orientation is changed during atreatment procedure, which may indicate a possible deviation from anexpected lesion profile.

FIGS. 23F-1, 23F-2 and 23F-3 illustrate various embodiments of output ona graphical user interface (for example, of a display on aradiofrequency generator or a computing device communicatively coupledto the one or more processors of the energy delivery system). Asillustrated, the output may include three radio buttons 23105, eachhaving a label 23110 identifying one of the orientation options (e.g.,perpendicular, oblique and parallel). In some embodiments, the radiobutton corresponding to the determined orientation may be marked ordifferentiated from the other radio buttons (e.g., have a lit upappearance as illustrated by the rays emanating from one of the radiobuttons in FIG. 23F). The marking may comprise a filling in of therespective radio button, highlighting of the respective radio button orchanging of a color of the respective radio button. In one embodiment,the radio buttons may appear as LEDs and the LED corresponding to thedetermined orientation may be changed to a green color or otherwise “litup” to signal the determined orientation. The output may also include agraphical image 23115 of an electrode icon or the distal end of themedical instrument in the determined orientation. As shown, the outputmay also include a graphical image of an arrow oriented according to thedetermined orientation. FIG. 23F-1 illustrates an example output when aparallel orientation is determined, FIG. 23F-2 illustrates an exampleoutput when an oblique orientation is determined and FIG. 23F-3illustrates an example output when a perpendicular orientation isdetermined. The radio buttons may be replaced with checkboxes or othervisual indicators.

Contact Sensing

According to some embodiments, various implementations of electrodes(e.g., radiofrequency or RF electrodes) that can be used forhigh-resolution mapping and radiofrequency ablation are disclosedherein. For example, as discussed in greater detail herein, an ablationor other energy delivery system can comprise a high-resolution, orcombination electrode, design, wherein the energy delivery member (e.g.,radiofrequency electrode, laser electrode, microwave transmittingelectrode) comprises two or more separate electrodes or electrodemembers or portions. As also discussed herein, in some embodiments, suchseparate electrodes or electrode portions can be advantageouslyelectrically coupled to each other (e.g., to collectively create thedesired heating or ablation of targeted tissue). In various embodiments,the combination electrode, or composite (e.g., split-tip), design may beleveraged to determine whether or not one or more portions of theelectrodes or other energy delivery members are in contact with tissue(e.g., endocardial tissue) and/or whether or not contacted tissue hasbeen ablated (e.g., to determine whether the tissue is viable or not).

Several embodiments of the invention are particularly advantageousbecause they include one, several or all of the following benefits: (i)confirmation of actual tissue contact that is easily ascertainable; (ii)confirmation of contact with ablated vs. unablated (viable) tissue thatis easily ascertainable; (iii) low cost, as the invention does notrequire any specialized sensor; (iv) does not require use of radiometry;(v) provides multiple forms of output or feedback to a user; (vi)provides output to a user without requiring the user to be watching adisplay; and/or (vii) provides safer and more reliable ablationprocedures.

With reference to FIG. 1, according to some embodiments, the deliverymodule 40 includes a processor 46 (e.g., a processing or control device)that is configured to regulate one or more aspects of the treatmentsystem 10. The delivery module 40 can also comprise a memory unit orother storage device 48 (e.g., non-transitory computer readable medium)that can be used to store operational parameters and/or other datarelated to the operation of the system 10. In some embodiments, theprocessor 46 comprises or is in communication with a contact sensingand/or a tissue type detection module or subsystem. The contact sensingsubsystem or module may be configured to determine whether or not theenergy delivery member(s) 30 of the medical instrument 20 are in contactwith tissue (e.g., contact sufficient to provide effective energydelivery). The tissue type detection module or subsystem may beconfigured to determine whether the tissue in contact with the one ormore energy delivery member(s) 30 has been ablated or otherwise treated.In some embodiments, the system 10 comprises a contact sensing subsystem50. The contact sensing subsystem 50 may be communicatively coupled tothe processor 46 and/or comprises a separate controller or processor andmemory or other storage media. The contact sensing subsystem 50 mayperform both contact sensing and tissue type determination functions.The contact sensing subsystem 50 may be a discrete, standalonesub-component of the system (as shown schematically in FIG. 1) or may beintegrated into the energy delivery module 40 or the medical instrument20. Additional details regarding a contact sensing subsystem areprovided below.

In some embodiments, the processor 46 is configured to automaticallyregulate the delivery of energy from the energy generation device 42 tothe energy delivery member 30 of the medical instrument 20 based on oneor more operational schemes. For example, energy provided to the energydelivery member 30 (and thus, the amount of heat transferred to or fromthe targeted tissue) can be regulated based on, among other things, thedetected temperature of the tissue being treated, whether the tissue isdetermined to have been ablated, or whether the energy delivery member30 is determined to be in contact (e.g., “sufficient” contact, orcontact above a threshold level) with the tissue to be treated.

With reference to FIG. 24, the distal electrode 30A may be energizedusing one or more conductors (e.g., wires, cables, etc.). For example,in some arrangements, the exterior of an irrigation tube comprisesand/or is otherwise coated with one or more electrically conductivematerials (e.g., copper, other metal, etc.). Thus, the one or moreconductors can be placed in contact with such a conductive surface orportion of the irrigation tube to electrically couple the electrode orelectrode portion 30A to an energy delivery module (e.g., energydelivery module 40 of FIG. 1). However, one or more other devices and/ormethods of placing the electrode or electrode portion 30A in electricalcommunication with an energy delivery module can be used. For example,one or more wires, cables and/or other conductors can directly orindirectly couple to the electrodes, without the use of the irrigationtube. The energy delivery module may be configured to deliverelectromagnetic energy at frequencies useful for determining contact(e.g., between 5 kHz and 1000 kHz).

FIG. 24 schematically illustrates one embodiment of a combination, orcomposite (e.g., split-tip), electrode assembly that can be used toperform contact sensing or determination by measuring the bipolarimpedance between the separated electrodes or electrode portions 30A,30B at different frequencies. Resistance values may be determined fromvoltage and current based on Ohm's Law: Voltage=Current*Resistance, orV=IR. Accordingly, resistance equals voltage divided by current.Similarly, if the impedance between the electrodes is complex, thecomplex voltage and current may be measured and impedance (Z) determinedby V_complex=I_complex*Z_complex. In this case, both magnitude and phaseinformation for the impedance can be determined as a function offrequencies. The different frequencies may be applied to the composite(e.g., split-tip) electrode assembly by an energy delivery module (e.g.,by energy generation device 42 of energy delivery module 40 of FIG. 1)or a contact sensing subsystem (such as contact sensing subsystem 50 ofsystem 10 of FIG. 1). Because the voltage and current values may beknown or measured, the resistance and/or complex impedance values can bedetermined from the voltage and current values using Ohm's Law. Thus,the impedance values may be calculated based on measured voltage and/orcurrent values in accordance with several embodiments rather thandirectly obtaining impedance measurements.

FIG. 25A is a plot showing resistance, or magnitude impedance, values ofblood (or a blood/saline combination) and of cardiac tissue across arange of frequencies (5 kHz to 1000 kHz). The impedance values arenormalized by dividing the measured impedance magnitude by the maximumimpedance magnitude value. As can be seen, the normalized impedance ofblood (or a blood/saline combination) does not vary significantly acrossthe entire range of frequencies. However, the normalized impedance ofcardiac tissue does vary significantly over the range of frequencies,forming a roughly “s-shaped” curve.

In one embodiment, resistance or impedance measurements can be obtainedat two, three, four, five, six or more than six different discretefrequencies within a certain range of frequencies. In severalembodiments, the range of frequencies may span the range of frequenciesused to ablate or otherwise heat targeted tissue. For example,resistance or impedance measurements may be obtained at two differentfrequencies f₁ and f₂ within the range of frequencies, where f₂ isgreater than f₁. Frequency f₁ may also be below the ablation frequencyrange and f₂ may be above the ablation frequency range. In otherembodiments, f₁ and/or f₂ can be in the range of ablation frequencies.In one embodiment, f₁ is 20 kHz and f₂ is 800 kHz. In variousembodiments, f₁ is between 10 kHz and 100 kHz and f₂ is between 400 kHzand 1000 kHz. By comparing the impedance magnitude values obtained atthe different frequencies, a processing device (e.g., a contact sensingsubsystem or module coupled to or executable by processor 46 of FIG. 1)can determine whether or not the electrode portion 30A is in contactwith issue (e.g., cardiac tissue) upon execution of specific program(machine-readable) instructions stored on a non-transitorycomputer-readable storage medium. The processing device is adapted tocommunicate with and execute modules (for example, a contact sensingmodule) for processing data, wherein the modules are stored in a memory.The modules may comprise software in the form of an algorithm ormachine-readable instructions.

For example, if the ratio r of an impedance magnitude value obtained atthe higher frequency f₂ to the impedance magnitude value obtained at thelower frequency f₁ is smaller than a predetermined threshold, theprocessing device may determine that the electrode portion 30A is incontact with cardiac tissue or other target region (e.g., upon executionof specific program instructions stored on a non-transitorycomputer-readable storage medium). However, if the ratio r of animpedance magnitude value obtained at the higher frequency f₂ to theimpedance magnitude value obtained at the lower frequency f₁ is greaterthan a predetermined threshold, the processing device may determine thatthe electrode portion 30A is not in contact with cardiac tissue butinstead is in contact with blood or a blood/saline combination. Thecontact determinations may be represented as follows:

${\frac{r_{f\; 2}}{r_{f\; 1}} < {threshold}} = {CONTACT}$${\frac{r_{f\; 2}}{r_{f\; 1}} > {threshold}} = {NO\_ CONTACT}$

In various embodiments, the predetermined threshold has a value between0.2 and less than 1 (e.g., between 0.2 and 0.99, between 0.3 and 0.95,between 0.4 and 0.9, between 0.5 and 0.9 or overlapping ranges thereof).

In various embodiments, resistance or impedance measurements areperiodically or continuously obtained at the different frequencies(e.g., two, three, four or more different frequencies) by utilizing asource voltage or current waveform that is a multi-tone signal includingthe frequencies of interest, as shown in FIG. 25B. The multi-tone signalor waveform may be sampled in the time-domain and then transformed tothe frequency domain to extract the resistance or impedance at thefrequencies of interest, as shown in FIG. 25C. In some embodiments,measurements or determinations indicative of contact may be obtained inthe time domain instead of the frequency domain. Signals or waveformshaving different frequencies may be used. In accordance with severalembodiments, performing the contact sensing operations is designed tohave little or no effect on the electrogram (EGM) functionality of thecombination, or composite (e.g., split-tip), electrode assembly. Forexample, common mode chokes and DC blocking circuits may be utilized inthe path of the impedance measurement circuitry as shown in FIG. 25D.The circuitry may also include a reference resistor R to limit themaximum current flow to the patient, as well as dual voltage samplingpoints V1 and V2 to enhance the accuracy of the impedance measurements.Additionally, a low-pass filter circuit (with, for example, a cut-offfrequency of 7 kHz) may be utilized in the path of the EGM recordingsystem, as shown in FIG. 4D. In several embodiments, all or portions ofthe circuitry shown in FIG. 25D are used in a contact sensing subsystem,such as contact sensing subsystem 50 of FIG. 1 or contact sensingsubsystem 4650 of FIG. 27. The frequencies used for contact sensing maybe at least greater than five times, at least greater than six times, atleast greater than seven times, at least greater than eight times, atleast greater than nine times, at least greater than ten times the EGMrecording or mapping frequencies. The contact sensing subsystem may becontrolled by a processing device including, for example, ananalog-to-digital converter (ADC) and a microcontroller (MCU). Theprocessing device may be integral with the processing device 46 of FIG.1 or may be a separate, stand-alone processing device. If a separateprocessing device is used, the separate processing device may becommunicatively coupled to the processing device 46 of FIG. 1.

In various embodiments, resistance or impedance measurements (e.g.,total impedance or component parts of complex impedance) areperiodically or continuously obtained at the different frequencies(e.g., two or three different frequencies) by switching between thedifferent frequencies. In accordance with several embodiments,performing the contact sensing operations may be designed to have littleor no effect on the electrogram (EGM) functionality of the combinationelectrode, or composite (e.g., split-tip), assembly. Accordingly,switching between the different frequencies may advantageously besynched to zero crossings of an AC signal waveform, as illustrated inFIG. 26A. In some embodiments, if the frequency switching does not occurat zero crossings, artifacts may be induced in the electrograms, therebydegrading the quality of the electrograms. In some embodiments,impedance measurements (e.g., bipolar impedance measurements) areobtained at multiple frequencies simultaneously. In other embodiments,impedance measurements are obtained at multiple frequenciessequentially.

In another embodiment, contact sensing or determination is performed byobtaining resistance or impedance measurements across a full range offrequencies from an f_(min) to an f_(max) (e.g., 5 kHz to 1 MHz, 10 kHzto 100 kHz, 10 kHz to 1 MHz). In such embodiments, the variation in thefrequency response, or the impedance measurements over the range offrequencies, is indicative of whether the electrode portion 30A is incontact with tissue (e.g., cardiac tissue) or not.

The impedance measurements may be applied to a model. For example, afrequency response function r(f) may be created and fit to a polynomialor other fitting function. The function may take the form, for example,of:

r(f)=a·f ³ +b·f ² +c·f+d

where a, b, c and d are the terms for the polynomial function that matchthe response of r(f) to measured data. Thresholds may then be set on thepolynomial terms to determine whether or not the electrode is in contactwith tissue. For example, a large d term may indicate a large impedanceindicative of tissue contact. Similarly, a large c term may indicate alarge slope in the impedance which is also indicative of tissue contact.The higher-order terms may be utilized to reveal other subtledifferences in the impedance response that indicate tissue contact.

In some embodiments, a circuit model such as that shown in FIG. 26B isused to determine the frequency response function r(f). The model maycomprise resistors and capacitors that predict the response of tissueand the tissue to electrode interfaces. In this approach, the R and Cvalues may be determined that best fit the measured data and thresholdsmay be utilized based on the R and C values to determine whether or notthe electrode is in contact with tissue. For example a small value ofcapacitance (C2) may indicate a condition of tissue contact, while alarge value may indicate no contact. Other circuit configurations arealso possible to model the behavior of the electrode impedance asdesired and/or required.

In some embodiments, the contact sensing or contact determinationassessments are performed prior to initiation of ablative energydelivery and not performed during energy delivery. In this case,switching may be utilized to separate the contact impedance measurementcircuitry from the ablative energy, as shown in FIG. 26C. In thisimplementation, a switch SW1 is opened to disconnect the composite(e.g., split-tip) capacitor (C_(ST)) and allow measurement of impedancein the higher frequency ranges where C_(ST) might present a shortcircuit (or low impedance in parallel with the measurement). At the sametime, switches SW2 and SW3 are set to connect to the impedancemeasurement circuitry, or contact sensing subsystem. As shown in FIG.26C, the impedance measurement circuit, or contact sensing subsystem, isthe same as that shown in FIG. 25D. When ablations are to be performed,SW2 and SW3 connect the tip electrodes to the ablative energy source(e.g., RF generator labeled as RF in FIG. 26C) and disconnect theimpedance measurement circuit. SW1 is also switched in order to connectthe composite (e.g., split-tip) capacitor C_(ST), thereby allowing thepair of electrodes to be electrically connected via a low impedancepath. In one embodiment, the split-tip capacitor C_(ST) comprises a 100nF capacitor that introduces a series impedance lower than about 4Ω at460 kHz, which, according to some arrangements, is a target frequencyfor radiofrequency ablation. As FIG. 26C also shows, the ablationcurrent path is from both electrodes to a common ground pad. Theimpedance measurement path is between the two electrodes, although othercurrent paths for the impedance measurement are also possible. In oneembodiment, the switch is a relay such as an electromechanical relay. Inother embodiments, other types of switches (e.g., solid-state, MEMS,etc.) are utilized.

In some embodiments, the contact sensing or contact determinationassessments described above may be performed while ablative energy orpower (e.g., ablative radiofrequency energy or power) is being deliveredbecause the frequencies being used for contact sensing are outside ofthe range (either above or below, or both) of the ablationfrequency(ies).

FIG. 27 schematically illustrates a system 4600 comprising ahigh-resolution, combination electrode, or composite (e.g., split-tip),electrode catheter, the system being configured to perform ablationprocedures and contact sensing or determination proceduressimultaneously. The high resolution (e.g., composite or split-tip)electrode assembly 4615 may comprise two electrodes or two electrodemembers or portions 4630A, 4630B separated by a gap. A separator ispositioned within the gap G, between the electrodes or electrodeportions 4630A, 4630B. The composite electrode assembly 4615 maycomprise any of the features of the high resolution (e.g., composite orsplit-tip) electrode assemblies described above in connection with FIG.2 and/or as otherwise disclosed herein. An energy delivery module (notshown, such as energy delivery module 40 of FIG. 1) or other signalsource 4605 may be configured to generate, deliver and/or apply signalsin an ablative range (e.g., radiofrequency energy 200 kHz-800 kHz, andnominally 460 kHz) while a contact sensing subsystem 4650 (such as thecontact sensing subsystem shown in FIG. 25D) delivers low-powersignal(s) 4607 (such as excitation signals) in a different frequencyrange (e.g., between 5 kHz and 1000 kHz) to be used to perform thecontact sensing or determination assessments to a composite electrodeassembly 4615. The low-power signal(s) 4607 may comprise a multi-tonesignal or waveform or separate signals having different frequencies. Thecontact sensing subsystem 4650 may comprise the elements shown in FIG.25D, as well as notch filter circuits to block the ablation frequency(e.g., a 460 kHz notch filter if a 460 kHz ablation frequency is used).In this configuration, a filter 4684 is utilized to separate the contactsensing frequencies and the ablation frequency(ies).

The filter 4684 may comprise, for example, an LC circuit element, or oneor more capacitors without an inductor. The elements and values of thecomponents of the filter 4684 may be selected to center the minimumimpedance at the center frequency of the ablative frequencies deliveredby the energy delivery module to effect ablation of targeted tissue. Insome embodiments, the filtering element 4684 comprises a singlecapacitor that electrically couples the two electrodes or electrodeportions 4630A, 4630B when radiofrequency current is applied to thesystem. In one embodiment, the capacitor comprises a 100 nF capacitorthat introduces a series impedance lower than about 4Ω at 460 kHz,which, according to some arrangements, is a target frequency forablation (e.g., RF ablation). However, in other embodiments, thecapacitance of the capacitor(s) or other band-pass filtering elementsthat are incorporated into the system can be greater or less than 100nF, for example, 5 nF to 300 nF, according to the operating ablationfrequency, as desired or required. In this case, the contact sensingimpedance frequencies would all be below the ablation frequency range;however, in other implementations, at least some of the contact sensingimpedance frequencies are within or above the ablation frequency range.

FIG. 28 illustrates a plot of impedance of an LC circuit elementcomprising the filter 4684, for example. As shown, the minimum impedanceis centered at the center frequency of the ablative RF frequencies (460kHz as one example) and the impedance is high at the frequencies in theEGM spectrum so as not to affect EGM signals or the contact sensingmeasurements. Additionally, the contact impedance measurements areperformed at frequencies that exist above and/or below the RF frequency(and above the EGM spectrum). For example, two frequencies f₁ and f₂ maybe utilized where f₁=20 kHz and f₂=800 kHz. At these frequencies, the LCcircuit would have a large impedance in parallel with the electrodes,thereby allowing the impedance to be measured. In one embodiment, theinductor L has an inductance value of 240 pH and the capacitor C has acapacitance value of 5 nF. However, in other embodiments, the inductor Lcan range from 30 μH to 1000 μH (e.g., 30 to 200 pH, 200 to 300 pH, 250to 500 pH, 300 to 600 pH, 400 to 800 pH, 500 to 1000 pH, or overlappingranges thereof) and the capacitor C can range from 0.12 nF to 3.3 μF(e.g., 0.12 to 0.90 nF, 0.50 to 1.50 nF, 1 nF to 3 nF, 3 nF to 10 nF, 5nF to 100 nF, 100 nF to 1 μF, 500 nF to 2 μF, 1 μF to 3.3 μF, oroverlapping ranges thereof). In various embodiments, f₁ is between 10kHz and 100 kHz and f₂ is between 400 kHz and 1000 kHz.

In accordance with several embodiments, the same hardware andimplementation as used for contact sensing may be used to determinetissue type (e.g., viable tissue vs. ablated tissue), so as to confirmwhether ablation has been successful or not. FIG. 29 is a plotillustrating resistance, or impedance magnitude, values for ablatedtissue, viable tissue and blood across a range of frequencies. As can beseen, the resistance of ablated tissue starts at a high resistance value(200Ω) and remains substantially flat or stable, decreasing slightlyover the range of frequencies. The resistance of blood starts at a lowerresistance (125Ω) and also remains substantially flat or stable,decreasing slightly over the range of frequencies. The resistance ofviable tissue, however, starts at a high resistance value (250Ω) andsignificantly decreases across the range of frequencies, roughly formingan “s-shaped” curve. The reason for the different resistance responsesbetween ablated and viable tissue is due, at least partially, to thefact that the viable cells (e.g., cardiac cells) are surrounded by amembrane that acts as a high-pass capacitor, blocking low-frequencysignals and allowing the higher-frequency signals to pass, whereas thecells of the ablated tissue no longer have such membranes as a result ofbeing ablated. The reason for the substantially flat response for bloodresistance is that most of the blood is comprised of plasma, which ismore or less just electrolytes having low impedance. The red blood cellsdo provide some variance, because they have similar membranes acting ascapacitors as the viable cardiac cells. However, because the red bloodcells constitute such a small percentage of the blood composition, theeffect of the red blood cells is not substantial.

Similar to the contact sensing assessments described above, resistance,or impedance magnitude, values may be obtained at two or morefrequencies (e.g., 20 kHz and 800 kHz) and the values may be compared toeach other to determine a ratio. In some embodiments, if the ratio ofthe impedance magnitude value at the higher frequency f₂ to theimpedance magnitude value at the lower frequency f₁ is less than athreshold, then the processing device (e.g., processing device 4624,which may execute a tissue type determination module for processingdata, wherein the module is stored in memory and comprises algorithms ormachine-readable instructions) determines that the contacted tissue isviable tissue and if the ratio of the impedance magnitude value at thehigher frequency f₂ to the impedance magnitude value at the lowerfrequency f₁ is greater than a threshold, then the processing device4624 determines that the contacted tissue is ablated tissue. In variousembodiments, the predetermined threshold has a value between 0.5 and 0.8(e.g., 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80).

In some embodiments, a combination of impedance magnitude differencesand differences in the ratio of impedance magnitudes at frequencies f₂and f₁ are utilized to determine both contact state (e.g., contact vs.in blood) as well as tissue type (e.g., viable tissue vs. ablatedtissue). In some embodiments, contact state and tissue typedeterminations are not performed during energy delivery or othertreatment procedures. In other embodiments, contact state and/or tissuetype determinations are performed during energy delivery or othertreatment procedures using filters and/or other signal processingtechniques and mechanisms to separate out the different frequencysignals.

In addition to the impedance magnitude, the same hardware andimplementation used for contact sensing (e.g., contact sensing subsystem50, 4650) may be utilized to compute the phase of the impedance (e.g.,complex impedance) across electrode portions. In one embodiment, thephase of the impedance may be added to algorithms for determiningdifferent contact states (e.g., contact vs. in blood) as well asdifferent tissue states (e.g., viable tissue vs. ablated tissue). FIG.30 shows an example of the phase of the impedance across electrodeportions versus frequency for viable tissue, ablated tissue and blood.The phase tends to be larger (closer to 0 degrees) for blood and smallerfor viable (unablated) tissue. For ablated tissue the phase may be inbetween blood and viable tissue. In one embodiment, a negative phaseshift at a single frequency indicates contact with tissue (either viableor ablated). A larger negative phase shift may indicate contact withviable tissue. In one embodiment, a phase of less than −10 degrees at800 kHz indicates contact with tissue (either viable or ablated). In oneembodiment, a phase of less than −20.5 degrees at 800 kHz indicatescontact with viable tissue. In other embodiments, the phase at otherfrequencies or combinations of frequencies are utilized to determinecontact state and tissue type. In some embodiments, the impedancemagnitude and phase are utilized together as vector quantities, anddifferences in the vectors for different frequencies are utilized todetermine contact state and tissue type.

In some embodiments, a combination of impedance magnitude differences,differences in the ratio of impedance magnitude values at frequencies f₂and f₁, and differences in the phase of the impedance are utilizedtogether to determine both contact state (e.g., contact vs. in blood) aswell as tissue type (e.g., viable tissue vs. ablated tissue). In oneembodiment, the determination process 5000 illustrated in FIG. 31 isutilized to determine both contact state as well as tissue type. In thisembodiment, an impedance magnitude threshold of 150Ω at 20 kHz isutilized to delineate between no contact and tissue contact (with alarger value indicating contact) at block 5005. Once contact isdetermined at block 5005, the ratio of the impedance magnitude at f₂=800kHz and f₁=20 kHz is computed at block 5010, with a value of less than0.6 indicating contact with unablated, or viable, tissue. If theaforementioned ratio is greater than 0.6, then the impedance phase at800 kHz is utilized at block 5015, and an (absolute) value greater than20.5 degrees indicates contact with ablated tissue. An (absolute) valueof less than 20.5 degrees indicates contact with unablated, or viable,tissue.

In some embodiments, the contact sensing subsystem 50 or system 10(e.g., a processing device thereof) analyzes the time-domain response tothe waveform described in FIG. 25B, or to an equivalent waveform. Inaccordance with several embodiments, contact sensing or tissue typedeterminations are based on processing the response to a signal appliedto a pair of electrodes or electrode portions (for example electrodepair 4630A, 4630B), the signal either including multiple frequencies orseveral frequencies applied sequentially. In some embodiments,processing device 4624 may process the response in time domain orfrequency domain. For example, given that blood is mostly resistive,with little capacitive characteristics, it is expected that time-domainfeatures such as rise or fall times, lag or lead times, or delaysbetween applied signal 4402 (e.g., I in FIG. 25D) and processed response4404 (e.g., V2 in FIG. 25D) will exhibit low values. Conversely, if theelectrode pair 4630A, 4630B of FIG. 27 is in contact with tissue, giventhat tissue exhibits increased capacitive characteristics, it isexpected that time-domain features such as rise or fall times, lag orlead times, or delays between applied signal 4402 (e.g., I in FIG. 25D)and processed response 4404 (e.g., V2 in FIG. 25D) will exhibit highervalues. An algorithm that processes parameters such as, but not limitedto, rise or fall times, lag or lead times, or delays between appliedsignal 4402 and processed response 4404 may indicate or declare contactwith tissue when the parameters exceed a threshold, or, conversely, itmay indicate or declare no contact with tissue when the parameters havevalues below a threshold. For example, assuming the signal 4402 isrepresented by a sinusoidal current of 800 kHz frequency, the algorithmcould declare contact with tissue if the response 4404 lags by more than0.035 μs. Conversely, the algorithm could declare lack of tissue contactif the response 4404 lags by less than 0.035 μs. Similarly, if thefrequency of signal 4402 were 400 kHz, the algorithm may decide:

-   -   no tissue contact, when the lag time is less than 0.07 ρs;    -   contact with ablated tissue, when the lag time is between 0.07        ρs and 0.13 ρs;    -   contact with viable or unablated tissue, when the lag time is        greater than 0.13 ρs.        The decision thresholds or criteria depend on the waveform of        signal 4402. Thresholds or decision criteria for other types of        waveforms may also be derived or determined.

In some embodiments, multiple inputs may be combined by a contactsensing or contact indication module or subsystem executable by aprocessor (e.g., processor of the contact sensing subsystems 50, 4650)to create a contact function that may be used to provide an indicationof contact vs. no contact, an indication of the amount of contact (e.g.,qualitative or quantitative indication of the level of contact, contactstate or contact force), and/or an indication of tissue type (e.g.,ablated vs. viable (non-ablated) tissue). For example, a combination of(i) impedance magnitude at a first frequency f₁, (ii) the ratio ofimpedance magnitudes at two frequencies f₂ and f₁ (defined as the slope)or the delta, or change, in impedance magnitudes at the two frequencies,and/or (iii) the phase of the complex impedance at the second frequencyf₂ are utilized together to create a contact function that is indicativeof contact state (e.g., tissue contact vs. in blood). Alternatively,instead of slope, a derivative of impedance with respect to frequencymay be used. In accordance with several embodiments, the impedancemeasurements or values comprise bipolar impedance measurements betweenthe pair of electrode members.

In one embodiment, a minimum threshold |Z|_(min) is defined for theimpedance magnitude at f₁, and a maximum threshold |Z|_(max) is definedfor the impedance at f₁. The impedance magnitude measured by the contactsensing subsystem 50, 650 at f₁ can be normalized such that theimpedance magnitude is 0 if the measured result is equal to |Z|_(min) orbelow, and the impedance magnitude is 1 if the measured result is equalto |Z|_(max) or above. Results in-between |Z|_(min) and |Z|_(max) may belinearly mapped to a value between 0 and 1. Similarly, a minimumthreshold S_(min) and a maximum threshold S_(max) may be defined for theslope (ratio of impedance magnitude between f₂ and f₁). If a derivativeof impedance with respect to frequency is used, then similar minimum andmaximum thresholds may be defined. The slope measured by the contactsensing subsystem 50 may be normalized such that the slope is 0 if themeasured result is equal to or above S_(min) and the slope is 1 if themeasured result is equal to or below S_(max). Results in between S_(min)and S_(max) may be linearly mapped to a value between 0 and 1. A minimumthreshold P_(min) and a maximum threshold P_(max) may also be definedfor the phase of the complex impedance at f₂. The phase measured by thecontact sensing subsystem 50 at f₂ may be normalized such that the phaseis 0 if the measured result is equal to or greater than P_(min) and 1 ifthe measured result is equal to or less than P_(max).

In accordance with several embodiments, the resulting three normalizedterms for magnitude, slope and phase are combined utilizing a weightingfactor for each. The sum of the weighting factors may be equal to 1 suchthat the resulting addition of the three terms is a contact indicatorthat goes from a zero to 1 scale. The weighted contact function (CF) canthus be described by the below equation:

${CF} = {{{WF}\; 1\frac{{Z}_{f\; 1} - {Z}_{\min}}{{Z}_{\max} - {Z}_{\min}}} + {{WF}\; 2\frac{S - S_{\min}}{S_{\max} - S_{\min}}} + {{WF}\; 3\frac{P_{f\; 2} - P_{\min}}{P_{\max} - P_{\min}}}}$

where |Z|_(f1) is the measured impedance magnitude at a first frequencyf₁, clipped to a minimum value of |Z|_(min) and a maximum value of|Z|_(max) as described above; S is the ratio of the impedance magnitudeat a second frequency f₂ to the magnitude at f₁, clipped to a minimumvalue of S_(min) and a maximum value of S_(max) as described above; andP_(f2) is the phase of the impedance at frequency f₂, clipped to aminimum value of P_(min) and a maximum value of P_(max) as describedabove. The weighting factors WF1, WF2 and WF3 may be applied to themagnitude, slope and phase measurements, respectively. As previouslystated, the weighting factors WF1+WF2+WF3 may sum to 1, such that theoutput of the contact function always provides a value ranging from 0to 1. Alternatively, values greater than 1 may be allowed to facilitategeneration of alerts to a user about circumstances when moretissue-electrode contact may become unsafe for patients. Such alerts maybe helpful in preventing application of unsafe levels of contact force.For example, CF values in the range of 1 to 1.25 may be flagged as a“contact alert” and may cause the contact sensing subsystem to generatean alert for display or other output to a user. The alert may be visual,tactile, and/or audible. The weighting factors may vary based oncatheter design, connection cables, physical patient parameters, and/orthe like. The weighting factors may be stored in memory and may beadjusted or modified (e.g., offset) depending on various parameters. Insome embodiments, the weighting factors may be adjusted based on initialimpedance measurements and/or patient parameter measurements.

The contact function described above can be optimized (e.g., enhanced orimproved) to provide a reliable indicator of the amount of contact withtissue (e.g., cardiac tissue, such as atrial tissue or ventriculartissue). The optimization may be achieved by defining minimum thresholdsZ_(min), S_(min) and P_(min) that correspond with no to minimal tissuecontact, as well as thresholds Z_(max), S_(max) and P_(max) thatcorrespond with maximal tissue contact. Weighting terms may also beoptimized (e.g., enhanced or improved) for robust responsiveness tocontact. In some embodiments, windowed averaging or other smoothingtechniques may be applied to the contact function to reduce measurementnoise.

As one example, at a frequency f₁=46 kHz and f₂=800 kHz, the valuesZ_(min)=115 ohms, Z_(max)=175 ohms, S_(min)=0.9, S_(max)=0.8,P_(min)=−5.1 degrees, P_(max)=−9 degrees, WF1=0.75, WF2=0.15, andWF3=0.1 are desirable (e.g., optimal) for representing the amount oftissue contact (e.g., for cardiac tissue of the atria or ventricles). Inother embodiments, Z_(min) may range from 90 ohms to 140 ohms (e.g., 90ohms to 100 ohms, 95 ohms to 115 ohms, 100 ohms to 120 ohms, 110 ohms to130 ohms, 115 ohms to 130 ohms, 130 ohms to 140 ohms, overlapping rangesthereof, or any value between 90 ohms and 140 ohms), Z_(max) may rangefrom 150 ohms up to 320 ohms (e.g., 150 ohms to 180 ohms, 160 ohms to195 ohms, 180 ohms to 240 ohms, 200 ohms to 250 ohms, 225 ohms to 260ohms, 240 ohms to 300 ohms, 250 ohms to 280 ohms, 270 ohms to 320 ohms,overlapping ranges thereof, or any value between 150 ohms and 320 ohms),S_(min) may range from 0.95 to 0.80 (e.g., 0.95 to 0.90, 0.90 to 0.85,0.85 to 0.80, overlapping ranges thereof, or any value between 0.95 and0.80), S_(max) may range from 0.85 to 0.45 (e.g., 0.85 to 0.75, 0.80 to0.70, 0.75 to 0.65, 0.70 to 0.60, 0.65 to 0.55, 0.60 to 0.50, 0.55 to0.45, overlapping ranges thereof, or any value between 0.85 and 0.45),P_(min) may range from 0 to −10 degrees (e.g., 0, −1, −2, −3, −4, −5,−6, −7, −8, −9, −10 or any combinations of ranges between, such as 0 to−5, −2 to −6, −4 to −8, −5 to −10), and P_(max) may range from −5 to −25degrees (e.g., −5 to −10, −7.5 to −15, −10 to −20, −15 to −25,overlapping ranges thereof or any value between −5 and −25 degrees). Theweighting factors WF1, WF2 and WF3 may cover the range from 0 to 1. Insome embodiments, values above or below the ranges provided may be usedas desired and/or required. Appropriate values for these parameters maybe dependent on the electrode geometry and frequencies f₁ and f₂ usedfor the measurements. Changes in the electrode geometry, physicalpatient parameters, connection cables, and frequencies may requiredifferent ranges for the above values.

In some treatment procedures, contact impedance measurements orcalculations (e.g., magnitude |Z|, slope S and/or phase P components ofbipolar contact impedance) may “drift” over time as liquid is infusedinto a patient prior to or during a treatment procedure. Examples ofliquid introduced during preparation for a treatment procedure or duringa procedure include, for example, saline, anesthetic drugs such aspropofol, blood thinners such as heparin, or other physiologicalliquids. The liquids can be introduced through the treatment device(e.g., ablation catheter) itself (e.g., saline through irrigation ports)and/or through IV infusion (IV fluid bags, tubing and syringes) or otherdelivery mechanisms. The introduction of liquids over time may affectthe resistivity and/or impedance of the blood over time, which, in turn,can affect contact impedance measurements or calculations determined bya contact sensing subsystem or module based on electrical measurements(e.g., voltage and current measurements or direct impedancemeasurements) between a pair of contact sensing electrodes (e.g.,between the pair of electrode members or portions of a composite tip(e.g., high-resolution or combination electrode) assembly as describedherein) over time. This drift over time due to changes in the bloodresistivity and/or impedance can affect the accuracy or reliability ofthe contact function or contact index determination (e.g., indicator ofquality of contact, level of contact or contact state) over time if notaccounted, or compensated, for. For example, electrophysiological salineis conductive and so as more saline is introduced into the vasculature,the patient's blood is diluted and the resistivity of the blood drops,causing a drift in the contact impedance measurements or calculationsover time. As a result, corrections to the contact functions oralgorithms may be desired to account, or compensate, for the drift,thereby improving the accuracy of the contact function or contact indexdeterminations or algorithms. For example, without compensation, thedrift may result in contact indication determinations (which may bedetermined based on static threshold values) that can substantially varyeven though the level of contact (e.g., contact force) remains steady,thereby providing inaccurate or unreliable contact level indication orassessment output and misleading a clinician as to the actual contactlevel.

Infusion rates are generally not constant or linear over time.Accordingly, look-up tables or set formulas based on flow rate and timeduration may not be used as reliably, in accordance with severalembodiments. Changes in blood resistivity could also be affected byfactors other than introduction of liquid and the techniques describedherein to counteract the drift due to introduction of liquid could alsobe used to account for changes in blood resistivity due to otherfactors, such as patient's body temperature, fluctuation in metabolicrates, etc.

In some embodiments, the thresholds in the contact functions oralgorithms, such as the thresholds |Z|_(max), |Z|_(min), S_(max),S_(min), P_(max), P_(min) in the weighted contact function providedabove, can advantageously be changed or adjusted from constant values tovalues that change based on one or more reference measurements. Forexample, if the contact impedance measurements are being measuredbetween a distal and proximal RF electrode member of a high-resolution,or combination, electrode assembly (such as a split-tip electrodeassembly) as described herein (which are likely in contact with targettissue such as cardiac tissue), a second set of reference measurementsmay be obtained between a different pair of reference electrodes thatare in the blood pool but are not expected to be in contact with tissue(or at least not in constant contact with tissue). In accordance withseveral embodiments, impedance measurements or values determined fromthe pair of reference electrodes when in blood change proportionally orsubstantially proportionally to the impedance measurements or valuesdetermined between the contact sensing electrodes when in blood or incontact with tissue (e.g., electrode portions of a composite tip, orcombination electrode, assembly). The impedance values determined fromthe reference electrodes do not have to be the same in an absolute senseas the impedance values of the contact sensing electrodes. A correctionfactor, or scaling value, can be applied as long as the drift for thereference electrodes proportionally or substantially proportionallytracks, or is otherwise indicative of, the drift for the contact sensingelectrodes. In some implementations, the drift between the impedancevalues of the reference electrodes and the drift of the impedance valuesof the contact sensing electrodes is within ±20% (e.g., within 20%,within 15%, within 10%, within 5%). In some embodiments, the pair ofreference electrodes may be positioned adjacent or proximate a targettreatment site (e.g., ablation site) but not in contact with tissue. Inother embodiments, the pair of reference electrodes are not positionedadjacent the target treatment site. In some embodiments, the pair ofreference electrodes are not positioned external to the patient and arenot within the medical instrument such that they cannot be exposed toblood.

FIG. 41A illustrates an ablation catheter having a composite tip (e.g.,high-resolution, or combination) electrode assembly comprised of adistal electrode member D1 and a proximal electrode member D2 separatedby a gap distance, as well as a distal ring electrode R1 and a proximalring electrode R2 that are positioned at a distance along the ablationcatheter proximal to the proximal electrode member D2 and that areseparated from each other by a separation distance. In variousembodiments, the separation distance between R1 and R2 (the distancebetween a proximal edge of R1 and a distal edge of R2) is between 0.5 mmand 3.5 mm (e.g., between 0.5 mm and 1.5 mm, between 1.0 and 3.0 mm,between 1.5 and 2.5 mm, between 2.0 and 3.5 mm, overlapping rangesthereof or any value within the recited ranges, including but notlimited to 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 2.5 mm, 3.0 mm, and3.5 mm). The separation distance between R1 and R2 (or other set ofreference electrodes) may be the same as the gap distance between D1 andD2 (or other set of contact sensing electrodes) may be different thanthe gap distance between D1 and D2. The distance between the proximaledge of D2 and the distal edge of R1 may range from 1 mm to 10 mm (e.g.,from 1.0 mm to 2.0 mm, from 2.0 to 3.0 mm, from 3.0 to 5.0 mm, from 4.0to 8.0 mm, from 5.0 to 10.0 mm, overlapping ranges thereof, or any valuewithin the recited ranges, including but not limited to 1.0 mm, 1.5 mm,2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, and 5.0 mm.

In some embodiments, the ring electrodes R1, R2 are used for mapping orother functions in addition to being used for reference measurements.The ring electrodes R1, R2, which are spaced proximal from the distaltip of the ablation catheter, tend not to be in contact with tissue (orat least are not in continuous contact with tissue) and instead are inthe blood/liquid mixture within a chamber, cavity, space or vessel ofthe heart, other organ or within vasculature adjacent to (e.g.,proximate or close to) the target tissue being treated. Accordingly, themeasurements obtained by the ring electrodes R1, R2 can serve aseffective reference measurements that can be used to track changes inthe impedance of blood as saline or other liquids are infused over time(and thus be used to adjust impedance measurements or calculations(e.g., magnitude, slope, and/or phase) that are used in qualitativecontact assessment functions or algorithms), thereby improving theaccuracy and/or reliability of the qualitative contact assessmentfunctions or algorithms. In some embodiments, reference measurements canbe obtained over a period of time and a minimum measurement value can beselected as the reference measurement in order to account for possibleinstances over the period of time when one or both of the ringelectrodes are in contact with tissue (e.g., when the ablation catheteris in a parallel or substantially parallel orientation). The ablationcatheter can include any of the structures or features described herein(e.g., filtering element and/or spacing between the D1 and D2 electrodemembers to facilitate high resolution mapping and ablative RF energydelivery, plurality of distributed temperature-measurement devices orsensors, thermal shunting structures, irrigation outlets, etc.).

FIG. 41B schematically illustrates an embodiment of a circuit connectionbetween the electrode members D1, D2 of the high resolution, orcombination, electrode assembly and the ring electrodes R1, R2 of theablation catheter of FIG. 41A and a contact sensing system or module,such as described herein. The contact sensing system or module may behoused, embodied or stored in a standalone component or within theenergy delivery module 40 (e.g., RF generator) or within the ablationcatheter itself. As shown in FIG. 41B, the circuit can include switchesSW1, SW2 to switch, or toggle, the connection to the contact sensingsystem or module between the ring electrodes R1, R2 for referencemeasurements and the electrode members D1, D2. Other alternativeconnection implementations may be used as desired and/or required.

As one example when a pair of proximal ring electrodes are used toobtain reference impedance measurements, a correction may be applied tothe |Z|_(max) threshold as follows:

|Z| _(max) _(_) _(adj) =|Z| _(max)*(1−A*(Z _(R1R2) _(_) _(initial) −Z_(R1R2) _(_) _(current))),

where |Z|_(max) is a baseline threshold that is valid when there is noinfusion of saline or other liquids, Z_(R1R2) _(_) _(initial) is aninitial baseline impedance value determined from one or more electricalmeasurements between the ring electrodes R1 and R2, Z_(R1R2) _(_)_(current) is a current impedance value determined from one or moreelectrical measurements between the ring electrodes R1 and R2, and A isa scaling factor.

A similar concept can be applied to the |Z|_(min) threshold:

|Z| _(min) _(_) _(adj) =Z _(min)*(1−B*(Z _(R1R2) _(_) _(initial) −Z_(R1R2) _(_) _(current))),

where Z_(min) is the baseline threshold that is valid when there is noinfusion of saline, Z_(R1R2) _(_) _(initial) and Z_(R1R2) _(_)_(current) are the same as previously described above, and B is ascaling factor.

An example of how this correction, or compensation, can be effected bythe contact sensing subsystem or module (e.g., upon execution ofspecific program instructions stored in memory by one or moreprocessors) is presented below with respect to an example bench test inwhich salinity level was adjusted over time. For simplicity, only themagnitude portion of the contact function, denoted CF1, will bedescribed. However, the same concept can also be utilized to compensatefor drift in the slope or the phase response as liquid is infused into apatient.

Table 2 below shows the response of |Z|_(f1) and CF1 vs Salinity Levelfor a realistic bench test with 5 g of contact force on cardiac tissue:

TABLE 2 Response of CF1 as Salinity Level increases, constant force of 5g applied. Salinity Level |Z|_(f1) CF1 1 224 2.8 2 218 2.6 3 210 2.3 4200 1.9 Contact Parameters: Zmax 230 Zmin 150

As can be seen in Table 2, as the salinity level increases past thebaseline (salinity level 1) the magnitude |Z|_(f1) begins to drop andCF1 begins to decrease—indicating reduced contact despite the contactforce being held constant at 5 g.

Table 3 below illustrates how the drift correction might be applied toaccount for this effect caused by changes in salinity level (which mayoccur due to introduction of liquid over time).

TABLE 3 Response of CF1 and CF1_adj with drift correction. DriftAdjustment Contact Parameters: Salinity Level Z_(R1R2) _(—) _(current)|Z|_(f1) Zmax_adj Zmin_adj CF1 CF1_adj Parameters: Z_(R1R2) _(—)_(initial) 152 1 152 224 230.0 150.0 2.8 2.8 Zmax 230 A 0.004 2 143 218221.7 141.9 2.6 2.9 Zmin 150 B 0.006 3 133 210 212.5 132.9 2.3 2.9 4 126200 206.1 126.6 1.9 2.8

In this embodiment, the reference measurement Z_(R1R2) _(_) _(current)is utilized with the technique described above to compute |Z|_(max) _(_)_(adj) and |Z|_(min) _(_) _(adj). In this embodiment, |Z|_(max) _(_)_(adj) is calculated as Z_(max)*(1−A*(Z_(R1R2) _(_) _(initial)−Z_(R1R2)_(_) _(current)) and |Z|_(min) _(_) _(adj) is calculated asZ_(min)*(1−B*(Z_(R1R2) _(_) _(initial)−Z_(R1R2) _(_) _(current)). Thesevalues for |Z|_(max) _(_) _(adj) and |Z|_(min) _(_) _(adj) can then beutilized to compute a drift-corrected value for CF1, denoted as CF1_adj.As shown in Table 3, the response of CF1_adj remains consistent as thesalinity level increases over time.

The above technique is an example of how drift correction can be appliedto impedance magnitude measurements or calculations as liquid is infusedinto a patient over time. The same concept can also be utilized tocompensate for drift in the slope or the phase response as liquid isinfused into a patient over time. In order to correct the slope or phaseresponse, the magnitude measurement between the ring electrodes R1 andR2 can be used in the same way described above. Additionally, the slopeor phase response measured or calculated across the ring electrodes R1and R2 may be utilized to create a drift correction.

In accordance with several embodiments, instead of using the ringelectrodes R1 and R2 for the reference measurements, the electrodemembers D1 and D2 of the high resolution, or combination, electrodeassembly can periodically be pulled into a non-contact position toconduct a reference measurement. Other combinations of pairs ofelectrodes other than two ring electrodes on the ablation catheter couldbe used to obtain reference measurements (e.g., R1 and D2, R1 and D1, R2and D1 or R2 and D2). Reference measurements could also be obtained fromother measurement devices or sources, as desired and/or required. Forexample, reference measurements could be obtained from a separate deviceother than the ablation catheter, such as a diagnostic catheter, amapping catheter, a coronary sinus catheter, and/or the like. The samedrift correction approach, or technique, described above when using thering electrodes for the reference measurement can be similarly appliedfor reference measurements obtained by the electrode members D1 and D2of the high resolution, or combination, electrode assembly or from anyother electrodes or other measurement devices or sources. The driftcorrection techniques described herein can be applied to contact sensingmeasurements or values obtained or determined by any pair of electrodesor electrode portions or other contact assessment members usingreference measurements or values obtained or determined by another pairof electrodes or electrode portions or other contact assessment members.The pairs of electrodes or electrode portions may be substituted withsingle members or with more than two members (e.g., three, four, five,six members). For example, although a two-electrode impedancemeasurement technique was described, three- or four-electrode impedancemeasurement techniques may be applied with equivalent results.

A method of correcting for drift in contact impedance measurements orcalculations (e.g., magnitude, slope, and/or phase components of bipolarcontact impedance measurements or calculations) comprises determining atleast one reference impedance value that can be used to adjustcorresponding threshold impedance component values of a contact qualityassessment function (e.g., the contact functions described herein) overtime. For example, the at least one reference impedance value can bedetermined from electrical measurements obtained using a pair ofelectrodes that are not likely to be in contact with tissue but arelikely to be in contact with the blood/liquid mixture adjacent theelectrodes or electrode portions being used to obtain contact impedancemeasurements for use in a contact quality assessment function or contactindication algorithm (such as those described herein), thereby providinga baseline that can be used to adjust contact impedance componentmeasurements to increase the accuracy and/or reliability of the contactquality assessment function or contact indication algorithm. In someembodiments, at least one reference impedance value can be obtained foreach threshold impedance component (e.g., magnitude at a firstfrequency, slope between magnitude at the first frequency and magnitudeat a second frequency, and phase at the second frequency) of the contactquality assessment function or contact indication algorithm. The methodmay further include adjusting the threshold impedance component valuesbased on the reference measurement(s). The adjustment may be performedcontinuously over time or at predefined time intervals (e.g., everytenth of a second, every half-second, every second, every two seconds,every three seconds, every four seconds, every five seconds, every tenseconds, every fifteen seconds, every twenty seconds).

The method may also include using the adjusted threshold impedancecomponent values in the contact quality assessment function or contactindication algorithm instead of the actual measured threshold impedancecomponent values by electrodes or electrode portions in contact withtissue. The method may be automatically performed by a contact sensingsubsystem or module (which may comprise, for example, programinstructions stored on a non-transitory computer-readable mediumexecutable by one or more processing devices and/or may comprisehardware devices, such as one or more microprocessors or centralprocessing units, memory (RAM or ROM), integrated circuit components,analog circuit components, digital circuit components and/ormixed-signal circuits) without transparency to a clinical professional.

In some embodiments, a contact function, or contact criterion, can bedetermined based, at least in part, on an if-then case conditionalcriterion. One example if-then case criterion is reproduced here:CC=IF(|Z_(MAG)|≥Z_(THR1), Best, IF(AND(Z_(THR1)≥|Z_(MAG)|,|Z_(MAG)|≥Z_(THR2)), Good, IF(AND(Z_(THR2)≥|Z_(MAG)|,|Z_(MAG)|≥Z_(THR3)), Medium, IF(AND(Z_(THR3)≥|Z_(MAG)|,|Z_(MAG)|≥Z_(THR4)), Low, No_Contact))))+IF(|Z_(MAG)|≥Z_(THR1), 0,IF(AND(SLOPE≤S_(THR1)), Good, IF(AND(S_(THR1)≤SLOPE, SLOPE≤S_(THR2)),Medium, IF(AND(S_(THR2)≤SLOPE, SLOPE≤S_(THR3)), Low,No_Contact))))+IF(|Z_(MAG)|≥Z_(THR1), 0, IF(AND(PHASE≤P_(THR1)), Good,IF(AND(P_(THR1)≤PHASE, PHASE≤P_(THR2)), Medium, IF(AND(P_(THR2)≤PHASE,PHASE≤P_(THR3)), Low, No_—Contact))))

FIG. 32 illustrates an embodiment of a contact criterion process 5100corresponding to the above if-then case conditional criterion. Thecontact criterion process 5100 may be executed by a processor uponexecution of instructions stored in memory or a non-transitorycomputer-readable storage medium. At decision block 5105, a measured orcalculated impedance magnitude value (e.g., based on direct impedancemeasurements or based on voltage and/or current measurements obtained bya combination electrode assembly comprising two electrode portions) iscompared to a predetermined threshold impedance. If the measured orcalculated impedance magnitude value |Z_(MAG)| is greater than a firstthreshold Z_(THR1) (e.g., 350Ω), then the Contact Criterion (CC) isassigned a “best” or highest value. If, however, the measured orcalculated impedance magnitude value |Z_(MAG)| is less than thethreshold Z_(THR1), then the process 5100 proceeds to block 5110, whereindividual subvalues for impedance magnitude, slope and phase aredetermined. At block 5115, the individual subvalues are combined (forexample summed) into an overall value indicative of contact state. Insome embodiments, the combination is a sum of a weighted combination, asdescribed above.

The process 5100 may optionally generate output at block 5120. Forexample, if at decision block 5105, the measured or calculated impedancemagnitude value |Z_(MAG)| is greater than the first threshold Z_(THR1),the process can generate an alert to a user that further manipulation ofthe catheter or other medical instrument may not further improve tissuecontact, but may instead compromise patient safety. For example, if theuser pushes too hard on the catheter or other medical instrument, theadditional pressure may achieve little improvement in tissue contact butmay increase the risk of tissue perforation (e.g., heart wallperforation). The output may comprise a qualitative or quantitativeoutput as described in further detail herein (for example in connectionwith FIG. 33).

FIG. 32A illustrates an embodiment of the individual subvalue subprocess5110 of process 5100 performed when the measured or calculated impedancemagnitude value |Z_(MAG)| is less than the first threshold Z_(THR1). TheContact Criterion (CC) overall value may be calculated by bracketing theimpedance magnitude (|Z_(MAG)|), the slope (S) and the phase (P) intointervals corresponding to good, medium, low and no contact levels.Subvalues corresponding to either good, medium, low or not contact aredetermined for each of the impedance magnitude, slope and phasecomponents depending on comparisons to various predetermined thresholdvalues. The subvalues may be combined to determine an overall contactstate value. In the example case conditional criterion above, the CC isa sum of the individual values received by each of the three parameters(|Z_(MAG)|, S, P) according to their corresponding level of contact(e.g., good, medium, low or no contact). For example, if Good=3,Medium=2, Low=1 and No_Contact=0 then the overall CC could be between0-2 for no or low contact, between 3-4 for poor contact, between 5-6 formedium contact and 7-9 for good contact. In one embodiment, when|Z_(MAG)| exceeds the first threshold Z_(THR1), then CC=10, as anindication that a “best,” or “optimal” level of tissue contact wasachieved. Other intervals or numbers can be used as desired.

In some embodiments, more than two frequencies are used (e.g., three orfour frequencies) for tissue contact or tissue type detection. Althoughthe computations described above were presented using impedancemagnitude, slope and phase, other characteristics of the compleximpedance may be used in other embodiments. For example, analyses of thereal and imaginary components of impedance may be used. Analyses ofadmittance parameters or scattering parameters may also be used. In someembodiments, direct analyses of the voltages and currents described inFIGS. 25A-27 (e.g., processing of voltage or current magnitudes,frequency changes or relative phase) may be used. Analyses of voltagesor currents may be performed in time domain or frequency domain.Impedance measurements, or values, may be calculated based on voltageand current measurements or may be directly measured. For example, phasemeasurements may comprise a difference in phase between measured voltageand measured current or may be actual impedance phase measurements.

In some embodiments, the contact indicator or contact function isassociated with output via an input/output interface or device. Theoutput may be presented for display on a graphical user interface ordisplay device communicatively coupled to the contact sensing subsystem50 (FIG. 1). The output may be qualitative (e.g., comparative level ofcontact as represented by a color, scale or gauge) and/or quantitative(e.g., represented by graphs, scrolling waveforms or numerical values)as shown in FIG. 33.

FIG. 33 illustrates an embodiment of a screen display 5200 of agraphical user interface of a display device communicatively coupled tothe contact sensing subsystem 50 (FIG. 1). The screen display 5200includes a graph or waveform 5210 illustrating impedance magnitude atfrequency f₁ over time, as well as a box 5211 indicating the real-timenumerical value of the impedance magnitude. The screen display 5100 alsoincludes a graph or waveform 5220 of slope (from f₂ to f₁) over time, aswell as a box 5221 indicating the real-time numerical value of theslope. The screen display 5200 further includes a graph or waveform 5230illustrating phase at frequency f₂ over time, as well as a box 5231indicating the real-time numerical value of the phase. The threemeasurements (magnitude, slope and phase) are combined into a contactfunction as described above and may be represented as a contact functionor indicator over time, as displayed on graph or waveform 5240. Thereal-time or instantaneous numerical value of the contact function mayalso be displayed (Box 5241).

In some embodiments, as shown in FIG. 33, the contact function orindicator may be represented as a virtual gauge 5250 that provides aqualitative assessment (either alone or in addition to a quantitativeassessment) of contact state or level of contact in a manner that iseasily discernable by a clinician. The gauge 5250 may be segmented into,for example, four segments, or regions, that represent differentclassifications or characterizations of contact quality or contactstate. For example, a first segment (e.g., from contact function valuesof 0 to 0.25) may be red in color and represent no contact, a secondsegment (e.g., from contact function values of 0.25 to 0.5) may beorange in color and represent “light” contact, a third segment (e.g.,from contact function values of 0.5 to 0.75) may be yellow in color andrepresent “medium” or “moderate” contact, and a fourth segment (e.g.,from contact function values of 0.75 to 1) may be green in color andrepresent “good”, or “firm”, contact. In other embodiments, fewer thanfour segments or more than four segments may be used (e.g., twosegments, three segments, five segments, six segments). In oneembodiment, three segments are provided, one segment for no contact orpoor contact, one segment for moderate contact and one segment for good,or firm, contact. The segments may be divided equally or otherwise asdesired and/or required. Other colors, patterns, graduations and/orother visual indicators may be used as desired. Additionally, a “contactalert” color or gauge graduation may be provided to alert the user aboutengaging the catheter or other medical instrument with too much force(e.g., contact function values greater than 1). The gauge 5250 mayinclude a pointer member that is used to indicate the real-time orinstantaneous value of the contact function on the gauge 5250.

In some embodiments, a qualitative indicator 5260 indicates whether ornot contact is sufficient to begin a treatment (e.g., ablation)procedure, the level of contact, tissue type, and/or whether contact isgreater than desired for safety. The qualitative indicator 5260 mayprovide a binary indication (e.g., sufficient contact vs. insufficientcontact, contact or no contact, ablated tissue or viable tissue) or amulti-level qualitative indication, such as that provided by the gauge5250. In one embodiment, the qualitative indicator 5260 displays thecolor on the gauge 5250 corresponding to the current contact functionvalue. Other types of indicators, such as horizontal or vertical bars,other meters, beacons, color-shifting indicators or other types ofindicators may also be utilized with the contact function to conveycontact quality to the user. Indicators may include one or morelight-emitting diodes (LEDs) adapted to be activated upon contact (or asufficient level of contact) or loss of contact. The LEDs may bedifferent colors, with each color representing a different level ofcontact (e.g., red for no contact, orange for poor contact, yellow formedium contact and green for good contact). The LED(s) may be positionedon the catheter handle, on a display or patient monitor, or any otherseparate device communicatively coupled to the system.

In one embodiment involving delivery of radiofrequency energy using aradiofrequency ablation catheter having a plurality oftemperature-measurement devices (such as the ablation catheters andtemperature-measurement devices described herein), the criterion fordetecting a loss of tissue contact during delivery of radiofrequencyenergy may be implemented as:

ΔT _(i) /Δt<−Threshold1  (Condition 1)

or

ΔT _(comp) /ΔP<Threshold2  (Condition 2)

where ΔT_(i) is the change in the temperature of any of the plurality oftemperature-measurement devices (e.g., sensors, thermocouples,thermistors) positioned along the catheter or other medical instrument;Δt is the interval of time over which the temperature change ismeasured; ΔT_(comp) is the change in the maximum of the temperatures ofthe temperature-measurement devices and AP is the change in appliedpower.

Condition 1 may signal that the temperature measurements obtained by thetemperature-measurement devices have dropped rapidly in a short periodof time, which may be indicative of a loss of contact or an insufficientor inadequate level of contact. For example, if ΔT_(i) is −10 degreesCelsius over a Δt of 1 second and Threshold1 is −5 degreesCelsius/second, then the contact loss condition is met (because −10degrees Celsius/second<−5 degrees Celsius/second).

Condition 2 may signal that the temperature of thetemperature-measurement devices is not increasing even though sufficientpower is being applied, which may be indicative of a loss of contact oran insufficient or inadequate level of contact. For example, ifΔT_(comp)=5 degrees Celsius and ΔP=30 Watts and if Threshold2 is 1degree Celsius/Watt, then the contact loss condition is met (because 5degrees Celsius/30 Watts<1 degree Celsius/Watt).

Electrical measurements (for example, impedance measurements, such asimpedance magnitude, impedance phase and/or or slope between impedancemagnitudes at different frequencies) obtained by contact detectionsubsystem or module (which may be, for example, within energy deliverymodule 40, such as a radiofrequency generator unit, or may be aseparate, standalone component) may be affected by hardware componentsin a network parameter circuit (for example, impedance circuit) ornetwork positioned between the contact detection subsystem or module andthe electrodes D1, D2 of a high-resolution electrode assembly, orsplit-tip electrode assembly, of an ablation catheter or other treatmentdevice. For example, different types (for example, brands, lengths,materials) of cables or wires may have different network parametersand/or other parameters that affect electrical measurements (forexample, voltage, current and/or impedance measurements) differently orcoiling of the cables or wires can affect electrical measurements. Inaddition, in some implementations, a catheter interface unit may beconnected at some point along the network parameter circuit (or mayreside in the electrical path) between the contact detection subsystemor module (for example, contact detection subsystem module) and theelectrodes or electrode portions D1, D2 of a high-resolution electrodeassembly, or split-tip electrode assembly, of an energy deliverycatheter or other treatment device. The catheter interface unit may ormay not comprise filters adapted for filtering signals having variousfrequencies (for example, low-pass filters, band-pass filters, high-passfilters implemented in hardware or software). As one example, thecatheter interface unit may comprise a hardware module or unit adaptedfor facilitating the connection of both a radiofrequency generator andan electroanatomical mapping system to a high resolution mapping andenergy delivery catheter having multiple electrode portions or members(devices (such as the ablation catheters or other energy delivery andtemperature-measurement devices described herein) is connected at somepoint along the network parameter circuit (for example, impedancemeasurement circuit) or otherwise resides in the electrical path of theseparated-apart electrode members. The presence or absence of a catheterinterface unit or other hardware module or unit, or differences in thenetwork parameters of cables, generators, or wires used may causevariations in the network parameters (for example, scattering parametersor electrical parameters such as impedance measurements dependingdirectly or from voltage and current measurements) or may result innetwork parameters (for example, electrical measurements or values suchas impedance measurements or values) that do not accurately reflect theactual network parameter value (for example, impedance) between twoelectrodes of a high-resolution electrode assembly, thereby resulting inless accurate and/or inconsistent contact indication values.Accordingly, the lack of accuracy or consistency may adversely affecttreatment outcomes or parameters and could have detrimental consequencesrelated to safety and/or efficacy. Thus, several embodiments aredisclosed herein to improve the accuracy and consistency of the networkparameter values (for example, electrical measurements such as impedancemagnitude, slope or phase values or voltage or current measurementvalues) obtained by an ablation system comprising a combinationelectrode assembly (for example, high-resolution, or split-tip,electrode arrangement of spaced-apart electrode members or portions).

In accordance with several embodiments, systems and methods forde-embedding, removing, or compensating for the effects caused byvariations in cables, generators, wires and/or any other component of anablation system (and/or components operatively coupled to an ablationsystem) or by the presence or absence of a catheter interface unit orother hardware component in an energy delivery and mapping system areprovided. In some embodiments, the systems and methods disclosed hereinadvantageously result in contact indication values that are based onnetwork parameter values (e.g., impedance values) that more closelyrepresent the actual network parameter value (e.g., impedance) acrossthe electrodes of the high resolution electrode assembly. Accordingly,as a result of the compensation or calibration systems and methodsdescribed herein, a clinician may be more confident that the contactindication values are accurate and are not affected by variations in thehardware or equipment being used in or connected to the system ornetwork parameter circuit. In some arrangements, the network parametervalues (e.g., impedance measurements) obtained by the system using thecompensation or calibration embodiments disclosed herein can be within±10% (e.g., within ±10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%) of the actualnetwork parameter values (e.g., impedance values) across the electrodemembers of the combination electrode assembly. For example, theimpedance magnitude, the impedance slope (ratio of impedance magnitudesat two frequencies) and phase of the impedance may each individually bemeasured to within +/−10% or better using this approach. As a result,the contact function or contact indicator can advantageously provide anaccurate representation of tissue contact, with an accuracy of +/−10% orgreater.

FIG. 34A illustrates a schematic block diagram of an embodiment of anetwork parameter measurement circuit 5400 (e.g., tissue contactimpedance measurement circuit). The network parameter measurementcircuit 5400 includes a contact sensing signal source 5405, a load 5410between two electrodes D1, D2 of a high-resolution electrode assembly ata distal end portion of an ablation catheter, and a chain of multipletwo-port networks representative of a generator 5415, catheter interfaceunit cables 5420A, 5420B, a catheter interface unit 5425, a generatorcable 5430 and catheter wires 5435. Because in some arrangements thenetwork parameter values (e.g., scattering parameter or electricalmeasurement such as voltage, current or impedance measurements) areobtained at the beginning of the chain at the level of the generator5415, the measured network parameter values (e.g., impedance valuesobtained directly or from voltage and/or current values) may differsignificantly from the actual network parameter values (e.g., impedancevalues) between the two spaced-apart electrode members D1, D2 due toeffects of the components of the network parameter circuit between thesignal source 5405 and the electrode members D1, D2. The impedancevalues may comprise impedance magnitude, slope between impedancemagnitude at different frequencies, and/or impedance phase values. Forexample, detected impedance magnitude at a frequency f₁ can be as muchas ±25% different than the actual impedance magnitude at a frequency f₁.Similarly, a detected slope (ratio of impedance magnitudes atfrequencies f₂ and f₁) can be as much as ±50% different than the actualslope. Additionally, the detected phase may be as much as ±−30 degreesdifferent than the actual phase. As a result of these combinedinaccuracies, a contact function (CF) or contact indication values maybe as much as −100% or +150% different than the intended contactfunction or contact indication values, thereby rendering the contactfunction ineffective in determining tissue contact. In accordance withseveral embodiments, the compensation or calibration embodimentsdisclosed herein can advantageously improve the accuracy of the contactfunction or contact indication values.

The network parameters of each of the multi-port (e.g., two-port)networks in the network parameter measurement circuit 5400 can beobtained (e.g., measured) and utilized to convert the measured networkparameter value (e.g., scattering parameter or electrical parameter suchas impedance) to a corrected (actual) value (e.g., impedance value). Insome embodiments, a two-port network analyzer is used to directlymeasure the scattering parameters (S-parameters) at the input and outputof each of the two-port networks. In other embodiments, multiplecomponents of the network parameter measurement circuit 5400 can becombined into groups of components and measured together. The networkparameters of the individual components or groups of components can becombined to determine an aggregate effect of the chain of two-portnetworks on the network parameter value(s). In some implementations, thescattering parameters of at least some of the components may behard-coded into a software program (e.g., using an average value basedon a few measurement samples) so as to reduce the number of measurementsto be taken or obtained.

According to one implementation, S-parameter matrices for each of thetwo-port networks or groups of two-port networks can be transformed toan overall transmission matrix. The overall transmission matrix may thenbe transformed back into S-parameters (or some other parameters) togenerate an S-parameter (or another type of) matrix for the totalnetwork. The S-parameters from the total S-parameter matrix can then beused to de-embed, calibrate or compensate for the S-parameters from themeasured input reflection coefficient to result in a corrected (actual)reflection coefficient. The actual reflection coefficient may then beconverted into a corrected impedance value that is more closelyindicative of the actual impedance between the two electrode portionsD1, D2 of a high-resolution electrode assembly. In several embodiments,the corrected impedance values are used as the inputs for the ContactFunction (CF) or other contact indication or level of contact assessmentalgorithm or function, as described above. For example, the correctedimpedance values can be used to determine the Z, S and P values in theweighted contact function (CF) described above.

The effects of the hardware components of the network parametermeasurement circuit (e.g., impedance measurement circuit) 5400 can becompensated for, de-embedded from, or calibrated so as to reduce orremove the effects of the hardware components or differences in thehardware components of a particular system (e.g., impedance measurementcircuit) setup prior to first use; however, the components of thenetwork parameter circuit may differ across different procedures asdifferent hardware components (e.g., generators, cables, cathetersand/or the like) are used or as a catheter interface unit or otherhardware component to facilitate electroanatomical mapping is plugged inor removed, thereby resulting in inconsistency if not compensated for.In some embodiments, the total system S-parameter matrix may only beupdated when the connections within the network parameter measurementcircuit 5400 change (e.g., when a catheter interface is plugged in orremoved from the electrical path, when a cable is switched, etc.).

In some embodiments, instead of requiring a manual de-embedding of theeffects on impedance of certain circuit components when connectionschange (which can be time-consuming and result in increased likelihoodof user error), the network parameters of a subset of the variouscomponents (e.g., the generator 5415, the catheter interface unit cables5420A, 5420B and the catheter interface unit 5425) are automaticallymeasured to enable the effects of these elements to be de-embedded fromthe network parameters (e.g., scattering parameters or impedancemeasurements) or otherwise compensated for or calibrated. FIG. 34Billustrates an embodiment of a circuit 5450 that can be used toautomatically de-embed or compensate for the effects of certain hardwarecomponents in the network parameter circuit 5400. In one embodiment, theauto-calibration circuit 5450 is positioned at a distal end of thecatheter interface unit cable before the generator cable 5430 andcatheter wires 5435. The circuit 5450 may advantageously provide theability to disconnect the electrode members D1, D2 of thehigh-resolution electrode assembly from the generator cable 5430 andcatheter 5435 and to connect a known load between D1 and D2.

In this embodiment, the auto-calibration circuit 5450 can assume thatthe network parameters of the generator cable 5430 and catheter wire5435 components are known and can be assumed to be constant. However, ifthe generator cable 5430 and/or catheter wires 5435 are determined tovary significantly from part to part, the circuit 5450 could beimplemented at the distal end of the generator cable 5430, in thecatheter tip or at any other location, as desired or required. In someembodiments, the known load of the auto-calibration circuit 5450includes a calibration resistor R_(cal) and a calibration capacitorC_(cal). Switches may be used to connect R_(cal) as the load, C_(cal) asthe load and both R_(cal) and C_(cal) in parallel as the load. Otherelements (such as inductors, combinations of resistors, inductors and/orcapacitors, or shorts or open circuits can be utilized as the knownload). As shown in FIG. 34B, the combined network parameters of thegenerator 5415, catheter interface unit cables 5420A, 5420B and thecatheter interface unit 5425 are represented as a single combinednetwork (Network 1).

In this embodiment, the network parameters (for example S-parameters) ofNetwork 1 are measured directly using the network parameter circuit andan S-parameter matrix is created from the network parameters. Each ofthe elements in the S-parameter matrix is a complex number and isfrequency dependent. The S-parameters may be measured at multipledifferent frequencies (e.g., 3 different frequencies in the kHz range,such as a first frequency from 5-20 kHz a second frequency from 25-100kHz and a third frequency from 500-1000 kHz). In one embodiment, thecomplex impedance is measured with the resistor R_(cal) connected andthe capacitor C_(cal) disconnected, with the capacitor C_(cal) connectedand the resistor R_(cal) disconnected and with both the resistor R_(cal)and the capacitor C_(cal) connected in parallel. The relationshipbetween the measured complex impedance, the S-parameters of Network 1and the known load can be expressed as three equations, which can thenbe used to solve for the S-parameters of Network 1. Once theS-parameters are characterized, they can be combined (e.g., using atransmission matrix approach) with the known network parameters of thegenerator cable 5430 and catheter wires 5435 to provide corrected(actual) impedance measurements at the distal end portion of thecatheter (e.g., across two spaced-apart electrode portions of acombination electrode assembly).

The automatic calibration techniques and systems described hereinadvantageously allow for increased confidence in the contact indicationvalues regardless of the generator, cables, catheter or other equipmentbeing used and regardless of whether a hardware component to facilitatesimultaneous electroanatomical mapping (e.g., a catheter interface unit)is connected. The various measurements may be performed automaticallyupon execution of instructions stored on a computer-readable storagemedium executed by a processor or may be performed manually.

The automatic calibration systems and methods described herein may alsobe implemented using an equivalent circuit model for one or morehardware components of the system (e.g., the generator circuitry, cableand catheter wiring). In such implementations, the equivalent circuitmodel comprises one or more resistors, one or more capacitors and/or oneor more inductors that approximate an actual response of the one or morehardware components being represented. As one example, a generator cablecomponent 5430 can be represented by a transmission-line equivalent RLCmodel as shown in FIG. 34C, where the measurement of the impedanceZ_(meas) would be performed at Port 1 with the actual (corrected)impedance Z_(act) desired being at Port 2. In this example, if theimpedance measurement circuit is measuring an impedance Z_(meas), theactual impedance measurement Z_(act) can be extracted by using circuitanalysis techniques. The equation relating the two impedances is givenby:

$Z_{meas} = {R + {j\; \omega \; L} + \frac{Z_{act}}{1 + {j\; \omega \; {C \cdot Z_{act}}}}}$

The actual values for R, L and C may be extracted from network parametermeasurements. For example if we measure the impedance (Z) parameters ofthis network, we can derive the following relationships:

${{{{{Z_{11} = \frac{V_{1}}{I_{1}}}}_{({{I\; 2} = 0})} = {R + {j\; \omega \; L} + \frac{1}{j\; \omega \; C}}}{Z_{21} = \frac{V_{2}}{I_{1}}}}}_{({{I\; 2} = 0})} = \frac{1}{j\; \omega \; C}$Z₁₁ − Z₂₁ = R + j ω L

where 1 and 2 denote the port numbers of the circuit, and V₁, I₁, V₂ andI₂ represent the voltages and currents at each of the respective ports.The values for R, L and C may also be measured utilizing measurementtools (e.g., a multimeter). The equivalent circuit model approachdescribed above is an example of this concept. In other implementations,more complex circuit models may be utilized to represent the variouselements of the system.

According to some arrangements, the high-resolution-tip electrodeembodiments disclosed herein are configured to provide localizedhigh-resolution electrograms (e.g., electrograms having a highlyincreased local specificity as a result of the separation of the twoelectrode portions and a high thermal diffusivity of the material of theseparator, such as industrial diamond). The increased local specificitymay cause the electrograms to be more responsive to electrophysiologicalchanges in underlying cardiac tissue or other tissue so that effectsthat RF energy delivery has on cardiac tissue or other tissue may beseen more rapidly and more accurately on the high-resolutionelectrograms. For example, the electrogram that is obtained using ahigh-resolution-tip electrode, in accordance with embodiments disclosedherein, can provide electrogram data (e.g., graphical output) 6100 a,6100 b as illustrated in FIG. 35. As depicted in FIG. 35, the localizedelectrograms 6100 a, 6100 b generated using the high-resolution-tipelectrode embodiments disclosed herein include an amplitude A1, A2.

With continued reference to FIG. 35, according to some embodiments, theamplitude of the electrograms 6100 a, 6100 b obtained usinghigh-resolution-tip electrode systems can be used to determine whethertargeted tissue adjacent the high-resolution-tip electrode has beenadequately ablated or otherwise treated. For example, according to someconfigurations, the amplitude A1 of an electrogram 6100 a in untreatedtissue (e.g., tissue that has not been ablated or otherwise heated,tissue that has not been ablated or otherwise heated to a desired orrequired threshold, etc.) is greater that the amplitude A2 of anelectrogram 6100 b that has already been ablated or otherwise treated.In some embodiments, therefore, the amplitude of the electrogram can bemeasured to determine whether tissue has been treated (e.g., treated toa desired or required level in accordance with a particular treatmentprotocol). For example, the electrogram amplitude A1 of untreated tissuein a subject can be recorded and used as a baseline. Future electrogramamplitude measurements can be obtained and compared against such abaseline amplitude in an effort to determine whether tissue has beenablated or otherwise treated to an adequate or desired degree.

In some embodiments, a comparison is made between such a baselineamplitude (A1) relative to an electrogram amplitude (A2) at a tissuelocation being tested or evaluated. A ratio of A1 to A2 can be used toprovide a quantitative measure for assessing the likelihood thatablation has been completed. In some arrangements, if the ratio (i.e.,A1/A2) is above a certain minimum threshold, then the user can beinformed that the tissue where the A2 amplitude was obtained has beenproperly ablated. For example, in some embodiments, adequate ablation ortreatment can be confirmed when the A1/A2 ratio is greater than 1.5(e.g., 1.5-1.6, 1.6-1.7, 1.7-1.8, 1.8-1.9, 1.9-2.0, 2.0-2.5, 2.5-3.0,values between the foregoing, greater than 3, etc.). However, in otherembodiments, confirmation of ablation can be obtained when the ratio ofA1/A2 is less than 1.5 (e.g., 1-1.1, 1.1-1.2, 1.2-1.3, 1.3-1.4, 1.4-1.5,values between the foregoing, etc.).

According to some embodiments, data which relate to tissue ablation orother tissue heating or treatment and which are collected, stored,processed and/or otherwise obtained or used by an ablation system can beintegrated with data obtained by one or more other devices or systems,such as, for example, a mapping system. As used herein, data is a broadterm and includes, without limitation, numerical data, textual data,image data, graphical data, unprocessed data, processed data and thelike. As discussed in greater detail herein, such integration of datacan be used to advantageously provide useful information to a physicianor other user (e.g. via a monitor or other output). For example, certaindata can be configured to be displayed in relation to various ablationor other heating points or locations that are visually depicted on amodel of the targeted region of a subject's anatomy (e.g., atrium, otherchamber or location of the heart, other tissue or organs, etc.). In someembodiments, such a model comprises a three-dimensional rendering orother model of the anatomy that is generated, at least in part, by amapping system. As used herein, mapping system is a broad term andincludes, without limitation, a three-dimensional (3D) electroanatomicalnavigation system, a rotor mapping system, other types of navigationand/or mapping devices or systems, an imaging device or system and/orthe like.

According to some embodiments, a mapping system (e.g., a 3Delectroanatomical navigation system, another type of device or systemthat is configured to generate a model of the anatomical structuressurrounding a particular anatomical location, etc.) is configured toreceive data and other information regarding an ablation procedure froma separate ablation or tissue treatment device or system (e.g., acatheter-based, RF ablation system, as disclosed herein) and/or anyother type of mapping device or system that is configured to facilitatea treatment procedure (e.g., a rotor mapping system, another imaging ormapping device, any other electrophysiology device or system, etc.). Inother embodiments, however, the ablation device or system is configuredto be integrated with a mapping system and/or one or more other mappingor other devices or system, as desired or required.

In embodiments where the mapping system is separate and distinct from anablation device or system and/or any other device or system, the mappingsystem can be configured to integrate with such other devices orsystems. For example, in some embodiments, the mapping system (e.g.,electroanatomical navigation system) can be designed and otherwiseadapted to receive data from a processor of a generator, other energydelivery module and/or any other component of an ablation system. Thus,the mapping system can include one or more processors, ports (e.g., forhardwired connection to and integration with the separatedevices/systems), wireless components (e.g., for hardwired connection toand integration with the separate devices/systems), filters,synchronization components or device and/or the like. In somearrangements, the mapping system (e.g., a 3D electroanatomicalnavigation system) can be configured to work with two or more differentablation devices or systems, as desired or required.

According to some embodiments, any of the ablation devices and systemsdisclosed herein, or equivalents thereof, can be configured to provideinformation to a user regarding one or more completed ablations (e.g.,ablation occurrences, spots or locations) along the targeted anatomy(e.g., cardiac tissue) of a subject. Such ablation data may include,without limitation, temperature, power, electrode orientation,electrode-tissue contact quality or amount (e.g. contact index orcontact force), etc. Such ablation data can be provided via integrationinto an existing mapping system (e.g., the EnSite™ Velocity™ CardiacMapping System by St. Jude Medical, Inc., CARTO® 3 EP System by BiosenseWebster, Inc, Rhythmia™ Mapping System by Boston Scientific, Inc., anyother electroanatomical navigation system, etc.). For example, in somearrangements, information collected by the ablation system during anablation procedure can be processed and integrated with mapping data(e.g. graphical output) of a separate 3D electroanatomical navigationsystem or other mapping system. In some embodiments, the graphicaloutput of the separate mapping system can be configured to create anddisplay a three-dimensional model of the targeted anatomical region(e.g., pulmonary veins, atrium, other chambers of the heart, otherorgans, etc.), the electrode and catheter itself, the located where anablation was performed and/or the like. In other embodiments, thecombined data are displayed on a monitor that is separate and districtfrom any portion or component of the separate mapping system. Forexample, the combined model or other graphical or textual representationcan be configured to be depicted on a display or output of the ablationsystem, an altogether separate monitor or output device (e.g., one thatis in data communication with the mapping system and/or the ablationsystem and/or the like).

In arrangements where a mapping system with a graphical user interfaceor other graphical output (e.g., that determines the 3D location of thecatheter or electrode and creates a three-dimensional view of thetargeted anatomical region being treated) is separate from a system thatreceives, processes, stores and otherwise manipulates data regarding thevarious ablations (e.g., ablation occurrences, points, spots, etc.)created by the an ablation device (e.g., a catheter with a RFelectrode), the two systems can be integrated or otherwise coupled toone another via one or more processors or control units. In someembodiments, such processors or control units can be included, at leastpartially, within the mapping system, within the ablation system, withinboth systems and/or one or more separate devices or systems, as desiredor required.

In some embodiments, the 3D location data, EGM activity data, rotormapping data, ablation data and/or any other data can be provided in asingle, stand-alone system that is configured to provide a graphicaloutput and other mapping data (e.g., EGM activity data, rotor mappingdata, etc.), and ablation data within the same user interface. Forexample, in some arrangements, such a stand-alone system can beconfigured to provide the graphical output and the ablation data withoutthe need for integration or other manipulation of data. In other words,in some embodiments, such a stand-alone system can be manufactured,assembled or otherwise provided to a user in a ready-to-use design.

FIG. 36A illustrates one embodiment of a graphical output 7000 providedto a user via a monitor, another type of display or any other outputdevice. Such a monitor or other output device can be configured to bepart of an ablation system. Alternatively, the output device can beseparate of an ablation system (e.g., a standalone device) or part of aseparate mapping system (e.g., 3D electroanatomical navigation system,other mapping device or system, etc.), another type of imaging orguidance system, etc. In such configurations, the output device can beadvantageously configured to operatively couple to an ablation system(e.g., the generator or other energy delivery module, a processor orcontroller, etc.).

As shown in FIG. 36A, the tip or distal portion of the ablation catheter7100 can be visible on the display or other output. As also illustratedin this embodiment, the various points along the targeted tissue (e.g.,cardiac tissue) that have been ablated can be depicted as circles, dotsor any other symbol or design. In some configurations, one or more othersymbols or representations other than circles or dots can be used todenote the locations where ablation or heating/treatment has beenperformed. For example, rectangles (e.g., squares), ovals, triangles,other polygonal shapes (e.g., pentagons, hexagons, etc.), irregularshapes and/or the like can be used, either in addition to or in lieu ofcircles.

In some embodiments, as illustrated in FIG. 36A, the monitor or otheroutput 7000 can be configured to display the orientation of the body ofthe subject being treated via a graphical representation 7010 of atorso. Accordingly, the user performing the procedure can bettervisualize and understand the anatomy that is mapped and indicated on theoutput.

Any other information or data can also be provided on the output 7000,either in addition to or in lieu of what is depicted in FIG. 36A. Forexample, in some embodiments, information or data displayed on theoutput can include, but not limited to, the date, time, duration and/orother temporal information regarding a procedure, the name and/or otherinformation about the subject being treated, the name and/or otherinformation about the physician and/or others conducting or assistingwith the procedure, the name of the facility and/or the like, as desiredor required.

According to some arrangements, as illustrated in FIGS. 36A and 36B, thegraphical representation of the ablations 7200 displayed on the monitoror other output 7000 can help ensure that a physician accurately createsa desired ablation or heating/treatment pattern in the targeted anatomy.For example, in some embodiments, the individual ablations form acircular or rounded pattern around one or more pulmonary veins of asubject (e.g., around the ostium of a single pulmonary vein, around theostia of two adjacent pulmonary veins, along the roofline betweenadjacent ostia, etc.). In other embodiments, as discussed in greaterdetail herein, the ablation pattern can be located along at least aportion of a heart chamber (e.g., atrium) to disrupt aberrant pathwaysalong or near the pulmonary veins (e.g., along one or more ostia of thepulmonary veins).

In some embodiments, information related to each ablation (e.g.,ablation instance, occurrence, point or location) 7200 of a series ofindividual ablations included in an ablation procedure can be providedto the user via the monitor other output 7000. By way of example,information can be provided to a user regarding an ablation 7200 whenthe user identifies a specific point or location. For example, in someembodiments, by manipulating a mouse, a touchpad and/or other device(e.g., the cursor or other pointing feature of such devices) on or neara particular ablation, a user can be provided with information regardingthat ablation point or location. In other embodiments, selecting aparticular ablation can be done by a user touching a specific portion ofa touchscreen with his or her finger. Regardless of how a specificablation is “selected” or otherwise “activated” by a user, the output(and the corresponding devices and/or systems to which the output areoperatively coupled) can be configured to provide certain data and/orother information regarding such a selected ablation. For instance, asillustrated in FIG. 37A, once a user “hovers” over or otherwise selectsa particular ablation 8202, a separate window 8300 (e.g., a pop-up orside window) can be displayed on the monitor or other output 8000.Further, according to some arrangements, once the user moves his or hercursor, finger and/or other selection device or feature away from aparticular ablation, the separate window 8300 can collapse or otherwisedisappear. In some embodiments, the pop-up or separate windows areconfigured to stay activated or otherwise visible for a particular timeperiod following selection or activation (e.g., for 0.5 to 5 seconds, 5to 10 seconds, longer than 10 seconds, time periods between theforegoing ranges, etc.), as desired or required. Advantageously, suchconfigurations can permit a user to quickly, easily and convenientlyreview data and other information regarding the procedure beingperformed using the ablation system.

In some embodiments, the manner by which ablation data, electricalactivity data (e.g., EGM activity data, rotor mapping data, etc.) and/orany other data are synchronized or linked to a specific can vary. Forexample, in some embodiments, ablation and/or other data can be capturedduring the time period (during the entire time period, some point intime during the time period, a subset of the time during the timeperiod, etc.) that an ablation is occurring (e.g., during the timeperiod when energy is being delivered from a generator or other energydelivery module to the electrode of the catheter). In someconfigurations, for example, a physician (and/or another individualassisting with a procedure, e.g., another physician, a technician, anurse, etc.) is able to commence and terminate such energy delivery viaone or more controllers (e.g., foot pedal, a hand-operated controller,etc.).

Therefore, according to some configurations, data from an ablationdevice or system (e.g., data captured, calculated, stored and/orotherwise processed by a generator or other component of the ablationdevice or system), data from a separate mapping system (e.g., a deviceor system used to obtain and process EGM activity data, rotor mappingdata, etc.) and/or the like is automatically provided to andsynchronized with one or more processors of another mapping system(e.g., a 3D electroanatomical navigation system), as noted herein. Suchsynchronization and integration can occur simultaneously with theexecution of an ablation procedure or once the procedure has beencompleted, as desired or required.

In other embodiments, however, the synchronization and integration ofdata between different devices and systems can be performed in otherways, either during or after the execution of an ablation procedure. Forexample, time logs between the different devices and systems can bealigned to extract the necessary data and other information from theablation system and/or any other separate system (e.g., a mapping systemconfigured to obtain and process EGM activity data) to “match up” orotherwise assign the necessary data to each ablation that is mapped bythe mapping system (e.g., the 3D electroanatomical navigation system).

According to some arrangements, the data and other information providedto a user in the pop-up windows on the display or other output devicecan be fixed or set by the manufacturer or supplier of the variouscomponents of the system (e.g., an integrated mapping/ablation system, astand-alone 3D electroanatomical navigation system, etc.). However, inother embodiments, the data and information can be customized by theuser, as desired or required. Accordingly, a user can choose the dataand information that is desired for a particular application or use.

In some embodiments, as illustrated in the embodiment of FIG. 37A, thedata and other information provided to the user (e.g., in a pop-up orother separate window 8300) by hovering over or otherwise selecting anablation 8202 can include, among other things, information (e.g.,graphical, textual, etc.) regarding the electrode's orientation relativeto targeted tissue 8310, contact information 8320 (e.g., a qualitativeor quantitative output relating to the level of contact between theelectrode and tissue as described in further detail herein), a graph orwaveform illustrating impedance measurements and determinations, slopemeasurements and determinations, phase measurements and determinations,a contact index or other calculation (e.g., based on various contactmeasurements such as, for instance, magnitude, slope and/or phase,etc.), temperatures curves/profiles (e.g., of targeted tissue overtime), electrogram amplitude reduction charts and/or data (e.g., per theconfigurations disclosed in FIG. 35) and/or the like, as desired orrequired.

With continued reference to FIG. 37A, the pop-up or separate window 8300related to an ablation 8202 includes a chart 8330 that plots tissuetemperature (e.g. composite tissue temperature from the variousthermocouples or other temperature sensors at or near the electrode),power and impedance over time. As noted in greater detail herein, suchinformation (e.g., whether in graphical or textual form) can be valuableto the physician performing an ablation procedure. For example, thephysician can quickly and conveniently hover over various ablations(e.g., ablation instances, points or locations) 8200, 8202 to ensurethat ablation of the targeted tissue has occurred according to his orher requirements and desires. In other embodiments, the pop-up orseparate window 8300 can include one or more other charts or plots, asdesired or required by a particular user or facility. For example, insome embodiments, the window includes a chart of the temperaturedetected by the various thermocouples or other sensors located at ornear the electrode over time (see, for example, FIGS. 22A, 22B, 23A and23B). In some embodiments, as illustrated in FIG. 37A, the separatewindow 8300 can include temperature measurements over time for each ofthe proximal and distal thermocouples (or other temperature sensors)included along the electrode. As shown, the temperature data can bepresented in graphical form to allow a practitioner to quickly andeasily compare the readings from different thermocouples. Such curves,either alone or together with other data and information provided viathe graphical representation of the output device, can ensure that thepractitioner maintains well informed during an ablation procedure. Forexample, such a graph of individual thermocouple trends can permit thepractitioner to assess whether desired or adequate contact between theelectrode and the targeted tissue is maintained during ablation. In somearrangements, for example, review of the individual thermocouples curvescan infer a clinical decision, such as, the quality of tissue contact,whether and when loss of contact or dislodgement occurred and/or thelike, as discussed in greater detail herein. Thus, in someconfigurations, the system can alert a user (e.g., visually, audibly,etc.) of such dislodgement or any other potentially undesirableoccurrence. In some embodiments, a separate display region, portion orarea 8350 of the window 8300 (and/or any other portion or area) can beprovided along the pop-up window 8300 to provide additional data orinformation to a user, such as, for example, EGM activity data, rotormap data, additional temperature data and/or the like.

In some embodiments, as noted herein, the pop-up or separate window 8300can be customizable by the user. Thus, for example, a user can choose(and between procedure or over time, modify) the graphical, textualand/or other data and information that is displayed in the pop-up window8300. In addition, various other features and characteristics related tothe pop-up window can be modified. For instance, the hover sensitivityof the system (e.g., how close a cursor, touching motion or otherselection method or technique needs to be to an ablation to activate thepop-up window), whether the user needs to click or otherwise manipulatea controller (e.g. mouse button, pressing a touchscreen, etc.) toactivate the pop-up window, how long the pop-up window stays activatedbefore disappearing from the monitor or other output device, the size,color and/or other general display features of the graphical and/ortextual information provided on the pop-up display (e.g., text font andsize, colors, etc.) and/or the like.

As noted in greater detail herein, in some embodiments, the contactfunction or indicator may be represented as a virtual gauge thatprovides a qualitative assessment (either alone or in addition to aquantitative assessment) of contact state or level of contact in amanner that is easily discernable by a clinician. Such a gauge can besegmented into, for example, four segments, or regions, that representdifferent classifications or characterizations of contact quality orcontact state. For example, a first segment (e.g., from contact functionvalues of 0 to 0.25) may be red in color and represent no contact, asecond segment (e.g., from contact function values of 0.25 to 0.5) maybe orange in color and represent “light” contact, a third segment (e.g.,from contact function values of 0.5 to 0.75) may be yellow in color andrepresent “medium” or “moderate” contact, and a fourth segment (e.g.,from contact function values of 0.75 to 1) may be green in color andrepresent “good”, or “firm”, contact. In other embodiments, fewer thanfour segments or more than four segments may be used (e.g., twosegments, three segments, five segments, six segments). In oneembodiment, three segments are provided, one segment for no contact orpoor contact, one segment for moderate contact and one segment for good,or firm, contact. The segments may be divided equally or otherwise asdesired and/or required. Other colors, patterns, graduations and/orother visual indicators may be used as desired. Additionally, a “contactalert” color or gauge graduation may be provided to alert the user aboutengaging the catheter or other medical instrument with too much force(e.g., contact function values greater than 1). The gauge may include apointer member that is used to indicate the real-time or instantaneousvalue of the contact function on the gauge. Such a gauge and/or othercontact data and information can be displayed in the pop-up window 8300.The contact index displayed may be determined using the drift correctiontechniques described herein based on reference measurements. Thereference measurements and the times they were obtained could also bedisplayed.

Additional data and/or information regarding an ablation can bedisplayed, either in lieu of or in addition to the foregoing. Forexample, the data and/or information can comprise, without limitation,information (e.g., graphical, textual, etc.) regarding the electrode'sorientation relative to targeted tissue, temperature data (e.g., tissuetemperature before, during and/or after ablation, the rate of change oftissue temperature during an ablation procedure, etc.), contactinformation (e.g., a qualitative or quantitative output relating to thelevel of contact between the electrode and tissue as described infurther detail herein, whether contact with previously ablated ornon-ablated tissue has been achieved, etc.), a graph or waveformillustrating impedance measurements and determinations, slopemeasurements and determinations, phase measurements and determinations,textual measurements of impedance, contact index or other calculations(e.g., based on various contact measurements such as, for instance,magnitude, slope and/or phase, etc.), temperatures curves/profiles(e.g., of targeted tissue over time), electrode orientation duringablation, applied RF power statistics (e.g. maximum and average power),electrogram amplitude reduction charts and/or data, mapping imagesand/or data, heart rate, blood pressure and other vitals of subjectduring the specific ablation, and/or the like.

According to some embodiments, the individual ablations depicted on amonitor or other output can be represented by symbols (e.g., circles,rectangles, other shapes, etc.) that are configured to vary in size(e.g., diameter, other cross-sectional dimension, etc.), color and/or inany other visually apparent manner, based on, at least in part, one ormore parameters associated with the ablation at the corresponding pointor location. By way of example, in some embodiments, the diameter of afirst ablation can be larger (e.g., proportionally ornon-proportionally) than the diameter of a second ablation when thefirst ablation is associated with a greater level of tissue ablation(e.g., greater size (e.g., deeper, longer, wider, larger area of impact,etc.), higher temperature of ablated tissue, longer duration of energyapplication, etc.). In some embodiments, the differences in size (e.g.,diameter) of the various ablations are proportional to one or moreablation characteristics, as listed above.

Another embodiment of a representation provided on a monitor or otheroutput device 8000′ is illustrated in FIG. 37B. As shown, the targetedanatomical area being treated has been mapped and is depicted in athree-dimensional model. Further, the various ablations 8200′ that havebeen conducted during a procedure can be illustrated relative to themapped tissue. In the depicted embodiment, such ablations are numberedor otherwise labeled (e.g., sequentially in the order of ablation).However, in other arrangements, the ablations 8200′ need not be labeled.As shown in FIG. 37B, in some configurations, information related to theablations (e.g., orientation, contact data, temperature curves, etc.)can be provided in a window or area 8300′ of the graphicalrepresentation 8000′ that remains on the monitor during an entiretreatment procedure. Thus, in some embodiments, unlike the features ofthe representation discussed above with reference to FIG. 37A, the dataand other information relating to the ablations is not provided in apop-up window. In some embodiments, the data and other informationprovided in window 8300′ pertains to a specific ablation 8202′ that thepractitioner or other user has selected (e.g. via hovering, depressionof a touchscreen and/or any other selection technique).

In some embodiments, as illustrated in FIG. 38, the graphicalrepresentation 9000 of the various ablations 9400 depicted on a monitoror other output can include graphical and/or textual data that areconfigured to be constantly visible (e.g., for a duration of an entireprocedure or at least longer than the relatively brief time period ofthe pop-up window configurations disclosed herein). Such arrangementscan be helpful to simultaneously provide to a physician or otherreviewer of the monitor or other output of the graphical representation9000 data and information about two or more (e.g., some or all)ablations of an ablation procedure. Thus, in some embodiments, aphysician can conveniently and easily assess (e.g., via a single image,without the need to activate separate pop-up windows or the like) thestatus of an ablation procedure. Further, in some arrangements, theconstantly-presented data and information can assist the physician inidentifying potential gaps in lesion formation (e.g., areas of targetedtissue that are non-ablated or under-ablated). As a result, the user cantarget such tissue areas to ensure a more complete and effectiveablation procedure.

With continued reference to FIG. 38, the orientation of the electrode(or other energy delivery member) located along a distal end of acatheter 9100 relative to skin at each ablation can be illustrated in asingle graphical representation 9000. As shown, in some arrangements,each ablation 9200 can include (e.g. within it, adjacent to it, etc.)one of three symbols 9400 that indicates whether the electrode was in aparallel, perpendicular or oblique orientation relative to tissue, inaccordance with the various determination methods and techniquesdisclosed herein.

In some embodiments, each ablation 9200 illustrated in a graphicalrepresentation 9000 can include an illustrated treatment area 9500 thatapproximates a zone or area of ablation (e.g., effective ablation,ablation that meets certain threshold requirements, etc.). For example,in some embodiments, such an area 9500 can identify the portion oftissue along each ablation 9200 that was heated above a targetedtemperature (e.g., 60 degrees C.) or some other threshold temperaturethat provides a level of comfort to the physician that sufficient tissueheating was accomplished, as desired or required for a particularprocedure or protocol. In some arrangements, the various treatment arearepresentations 9500 can be color coded (e.g., yellow for low heating,orange for medium heating, red for high heating, etc.) to provide moredetailed information to the physician. In other embodiments, such colorcoding can depend on approximated and/or actual tissue temperatures.Thus, the various treatment area representations 9500 associated witheach ablation can be color-coded (e.g., different colors, differentshades (e.g., gray-scale) or other color property levels, etc.)according to a temperature legend that may also be displayed.

With further attention to FIG. 38, regardless if or how the varioustreatment area representations 9500 surrounding the ablations 9200 arecolor-coded or otherwise distinguished, the graphical representation9000 can be configured to advantageously indicate areas or zones aroundor along the ablations 9200 where the heating or ablation effects ofadjacent ablations are compounded. Alternatively, as described ingreater detail herein (e.g., with reference to FIGS. 38 and 39),estimates or determinations of lesion depth, width or volume, may bedrawn and displayed as part of a graphical representation or otheroutput. For example, in FIG. 38, such regions or areas 9500 that includethe overlapping ablation/heating effects of two or more separateablations 9200 are illustrated in darker color. Overlapping may bedetermined or estimated based on lesion depth, width and volumeestimates, as explained herein (e.g., with reference to FIGS. 38 and39). Various other graphical representations, in addition to or lieu ofthose depicted herein, can be used to conveniently provide usefulinformation to a physician or other user or viewer of such systems abouta particular ablation procedure. Thus, as noted above, the physician canbetter assess the status of a procedure and, if necessary, conductsupplemental, well-targeted ablation to ensure a successful result.

In some embodiments, the graphical representation can be configured todisplay a pathway of a desired or required ablation pattern. Such apathway (not illustrated herein) can guide and otherwise assist thephysician in following a predictable, safe and efficacious ablation pathwhen conducting an ablation procedure. In certain arrangements, such adesired pathway can be illustrated as a line, points and/or in any othermanner that distinguishes it from other elements on the graphicalrepresentation 9000, as desired or required.

FIG. 39 illustrates a two-dimensional graph of ablation depth over aparticular ablation pathway. Such ablation depth data may be derived orestimated from electrode orientation, temperature, power, tissue-contactinformation and/or any other input. As discussed in Panescu et al.,“Three-Dimensional Finite Element Analysis of Current Density andTemperature Distributions During Radio-Frequency Ablation,” IEEETransaction on Biomedical Engineering, Vol. 42, No. 9 (September 1995),pp. 879-889, which is hereby incorporated by reference herein and madepart of the present specification, lesion depth and width depend onelectrode orientation, temperature and power, among other factors.Accordingly, a graphical representation or other output 9600 can beconfigured to incorporate such data in order to draw and estimate lesiondepth, width or volume profile, as desired or required. For example, insome embodiments, the ablation pathway can include a generallycircumferential path around a pair of pulmonary veins within the leftatrium of a subject (e.g., around the ostia of such veins). In somearrangements, as known in the art, such an ablation procedure can helpdisrupt aberrant conduction patterns in subjects with atrialfibrillation or other cardiac arrhythmias. Thus, either in combinationwith or in lieu of the ablation area approximations (as illustrated inFIG. 38), a system can be configured to determine (e.g., estimate inaccordance with various embodiments disclosed herein) the effectiveablation or targeted heating depth, width and/or volume along the tissuebeing treated. As shown in the graphical representation 9600 in FIG. 39,the system can illustrate the ablation depth 9650 as a function ofdistance along the treatment pathway. Such information can be displayed(e.g., continuously, intermittently (for example, as part of a pop-upwindow), etc.) together with an overall ablation representation, asshown in FIG. 37A or 37B or FIG. 38. Thus, a physician can beeffectively provided with a three-dimensional assessment associated withan ablation procedure, where both areal/spacial extent and depth ofablation (or desired heating) of tissue are graphically represented tohim or her during a procedure. In other embodiments, athree-dimensional, volumetric representation of ablated tissue can beprovided to the user that graphically combines areal extent and depthinto a single integrated image.

As noted herein, regardless of how data and other information related toa particular procedure is processed and displayed to a user, suchembodiments can be advantageous in easily and conveniently assessingpotential weak or clinically susceptible points or locations in aprocedure (e.g., identifying gaps along the tissue being treated).Accordingly, a physician or other user can use this valuable informationto ensure that more complete and thorough ablation procedures areconsistently performed. As discussed herein, for example, with theassistance of the various configurations disclosed herein, a physiciancan quickly identify regions of tissue along a desired ablation pathwaythat may not have been treated to a threshold level. Thus, such tissueregions can be targeted before an ablation procedure is completed toensure proper and efficacious treatment.

According to some embodiments, the system can be configured to identifyand highlight (e.g., automatically) potential or actual gaps (e.g.,potentially under-ablated or other susceptible tissue regions) andidentify (e.g., graphically, textually, etc.) such regions to the user.For example, in some embodiments, the system can highlight portions ofthe targeted anatomy that may not have been ablated properly (e.g.,regions where the length, width, depth of ablation or heating isinsufficient relative to some threshold). Such highlighting can take anydesired form, such as, for example, circling or otherwise drawing anoutline around such areas, coloring such regions with a different coloror other graphical pattern (e.g., cross-hatching) and/or the like.

In some embodiments, the ability of the system to determine and indicatepotential, likely or actual lesion gaps (e.g., potentially under-ablatedregions of the subject's anatomy being treated) can help ensure that apractitioner is alerted to such locations. Accordingly, the physiciancan evaluate and determine if any such regions exist, and if necessary(e.g., based on his or her expertise, experience and general approach)conduct additional ablations at various locations before a treatmentprocedure is completed. This can help ensure that practitionersconsistently and reliably complete an ablation procedure that willincrease the likelihood of clinical success.

In some embodiments, the mapping system (e.g., a 3D electroanatomicalnavigation system) can be configured to map a subject's cardiac chamber(e.g., atrium) during a cardiac fibrillation (e.g., atrial fibrillation)treatment. For example, the electroanatomical navigation system or othermapping system can be configured to obtain EGM activity data, rotormapping data and/or other electrical data. As noted herein such data canbe obtained from a mapping system that is also configured to obtain andprocess data that facilitate the 3D mapping and modeling of a targetedanatomical location (e.g., the left atrium of a subject). Alternatively,such data can be provided to the mapping system (e.g., theelectroanatomical navigation system) via a separate mapping device orsystem that is operatively coupled to the mapping system, as desired orrequired.

In some embodiments, subjects that indicate for atrial fibrillationexhibit an atrial fibrillation rotor pattern in their atrium that ischaracteristic of the disease. In some arrangements, electricallymapping the signals being transmitted through a subject's atrium, andthus, more accurately determining a map of the corresponding atrialfibrillation rotor that is cause of the disease, can assist with thesubject treatment of the subject. For example, in some embodiments, oncethe atrial fibrillation rotor is accurately mapped (e.g., using aseparate mapping device or system that is either integrated with oroperatively coupled to a 3D electroanatomical navigation system), apractitioner can more precisely treat the portions of the atrium thathelp treat the disease. This can provide several benefits to a subject,including more precise and accurate ablation that increases thelikelihood of effective treatment, less trauma to the subject as area orvolume of tissue that is ablated can be reduced and/or the like. Thus,in some embodiments, the use of the various embodiments described hereinthat provide detailed data and other information regarding the status ofan ablation procedure can be helpful in ensuring that targeted tissue isproperly ablated in view of the corresponding rotor map. This canprovide more reliable and efficacious treatment of atrial fibrillationand other cardiac arrhythmias.

As illustrated in the example 3D activation map of FIG. 40A, there existrelatively large gaps or spaces between adjacent electrodes of themulti-electrode device or system. As a result, the corresponding 3D mapthat is generated using only the multi-electrode mapping device orsystem may be inaccurate and/or incomplete. For example, in someembodiments, there may exist a rotor or other indicia of a cardiacarrhythmia (e.g., atrial fibrillation) or other condition that may notbe identified by the fixed-space electrodes of a multi-electrode mappingdevice or system.

By way of example, FIG. 40B illustrates a region 9920 of the subject'sanatomical space that has been mapped using a catheter-based device orsystem, either alone or in combination with one or more other mappingdevices or systems (e.g., a multi-electrode mapping system), inaccordance with the various embodiments disclosed herein. The map ofFIG. 40B provides additional mapping data between the set, fixedlocations of the electrodes in a multi-electrode device or system. Suchenhanced mapping systems and related methods (e.g., usinghigh-resolution electrode embodiments disclosed herein) could be used todetect the presence of a rotor 9930 (e.g., wherein a region of thetargeted anatomical region exhibits a localized area in which activationof said tissue forms a circular or repetitive pattern). Thus, thepresence of a condition can be accurately identified, and subsequentlytreated, using embodiments of the enhanced mapping devices or systemsdisclosed herein. As enumerated above, the embodiments disclosed hereincan be used to generate many types of enhanced cardiac maps, such as,without limitation: cardiac activation maps, cardiac activitypropagation velocity maps, cardiac voltage maps and rotor maps. Inaccordance with several embodiments, the enhanced mapping systemfacilitates more focused, localized or concentrated ablation targetsand/or may reduce the number of ablations required to treat variousconditions.

Accordingly, the ability to generate such enhanced cardiac maps canfurther enhance the various graphical representations presented herein(e.g., with reference to FIGS. 36A to 39) and can further improveablation systems and techniques that take advantage of such features.For example, in some embodiments, the identification of a rotor 9930 canbe superimposed or otherwise identified on a graphical representation ofan ablation map relative to a mapped region of the targeted anatomy, asdiscussed herein, e.g., with respect to the arrangements of FIGS. 36A to39. As a result, the physician conducting an ablation procedure can moreaccurately, reliably and efficaciously target the proper portions of thesubject's anatomy in an effort to treat the subject's condition (e.g.,atrial fibrillation, other cardiac arrhythmia or ailment, otherconduction-related malady, etc.).

In some embodiments, the system comprises one or more of the following:means for tissue modulation (e.g., an ablation or other type ofmodulation catheter or delivery device), means for generating energy(e.g., a generator or other energy delivery module), means forconnecting the means for generating energy to the means for tissuemodulation (e.g., an interface or input/output connector or othercoupling member), means for performing tissue contact sensing and/ortissue type determination, means for displaying output generated by themeans for performing tissue contact sensing and/or tissue typedetermination, means for determining a level of contact with tissue,means for calibrating network parameter measurements in connection withcontact sensing means, etc.

In some embodiments, the system comprises various features that arepresent as single features (as opposed to multiple features). Forexample, in one embodiment, the system includes a single ablationcatheter with a single high-resolution (e.g., composite, such assplit-tip) electrode and one or more temperature sensors (e.g.,thermocouples) to help determine the temperature of tissue at a depth.The system may comprise an impedance transformation network. In someembodiments, the system includes a single ablation catheter with a heatshunt network for the transfer of heat away from the electrode and/ortissue being treated. In some embodiments, the system includes a singlecontact sensing subsystem for determining whether there is and to whatextent there is contact between the electrode and targeted tissue of asubject. Multiple features or components are provided in alternateembodiments.

In one embodiment, the system comprises one or more of the following:means for tissue modulation (e.g., an ablation or other type ofmodulation catheter or delivery device), means for generating energy(e.g., a generator or other energy delivery module), and/or means forconnecting the means for generating energy to the means for tissuemodulation (e.g., an interface or input/output connector or othercoupling member), etc.

In some embodiments, the system comprises one or more of the following:means for tissue modulation (e.g., an ablation or other type ofmodulation catheter or delivery device), means for measuring tissuetemperature at a depth (e.g., using multiple temperature sensors (e.g.,thermocouples) that are thermally insulated from the electrode and thatare located along two different longitudinal portions of the catheter),means for effectively transferring heat away from the electrode and/orthe tissue being treated (e.g., using heat shunting materials andcomponents) and means for determining whether and to what extent thereis contact between the electrode and adjacent tissue (e.g., usingimpedance measurements obtained from a high-resolution electrode that isalso configured to ablate the tissue).

In some embodiments, the system comprises one or more of the following:an ablation system consists essentially of a catheter, an ablationmember (e.g., a RF electrode, a composite (e.g., split-tip) electrode,another type of high-resolution electrode, etc.), an irrigation conduitextending through an interior of the catheter to or near the ablationmember, at least one electrical conductor (e.g., wire, cable, etc.) toselectively activate the ablation member and at least one heat transfermember that places at least a portion of the ablation member (e.g., aproximal portion of the ablation member) in thermal communication withthe irrigation conduit, at least one heat shunt member configured toeffectively transfer heat away from the electrode and/or tissue beingtreated, a plurality of temperature sensors (e.g., thermocouples)located along two different longitudinal locations of the catheter,wherein the temperature sensors are thermally isolated from theelectrode and configured to detect temperature of tissue at a depth,contact detection subsystem for determining whether and to what extentthere is contact between the electrode and adjacent tissue (e.g., usingimpedance measurements obtained from a high-resolution electrode that isalso configured to ablate the tissue), etc.

In the embodiments disclosed above, a heat transfer member is disclosed.Alternatively, a heat retention sink is used instead of or in additionto the heat transfer member in some embodiments.

According to some embodiments, an ablation system consists essentiallyof a catheter, an ablation member (e.g., a RF electrode, a composite(e.g., split-tip) electrode, another type of high-resolution electrode,etc.), an irrigation conduit extending through an interior of thecatheter to or near the ablation member, at least one electricalconductor (e.g., wire, cable, etc.) to selectively activate the ablationmember and at least one heat transfer member that places at least aportion of the ablation member (e.g., a proximal portion of the ablationmember) in thermal communication with the irrigation conduit, at leastone heat shunt member configured to effectively transfer heat away fromthe electrode and/or tissue being treated and a plurality of temperaturesensors (e.g., thermocouples) located along two different longitudinallocations of the catheter, wherein the temperature sensors are thermallyisolated from the electrode and configured to detect temperature oftissue at a depth.

Any methods described herein may be embodied in, and partially or fullyautomated via, software code modules (e.g., in the form of an algorithmor machine readable instructions) stored in a memory orcomputer-readable medium executed by one or more processors or othercomputing devices. In embodiments involving multiple processors, theprocessors may operate in parallel to form a parallel processing systemin which a process is split into parts that execute simultaneously ondifferent processors of the ablation system. The methods may be executedon the computing devices in response to execution of softwareinstructions or other executable machine-readable code read from atangible computer readable medium. A tangible computer readable mediumis a data storage device that can store data that is readable by acomputer system. Examples of computer readable mediums include read-onlymemory (e.g., ROM or PROM, EEPROM), random-access memory, other volatileor non-volatile memory devices, CD-ROMs, magnetic tape, flash drives,and optical data storage devices. The modules described herein (forexample, the contact detection or sensing modules) may comprisestructural hardware elements and/or non-structural software elementsstored in memory (for example, algorithms or machine-readableinstructions executable by processing or computing devices).

In addition, embodiments may be implemented as computer-executableinstructions stored in one or more tangible computer storage media. Aswill be appreciated by a person of ordinary skill in the art, suchcomputer-executable instructions stored in tangible computer storagemedia define specific functions to be performed by computer hardwaresuch as computer processors. In general, in such an implementation, thecomputer-executable instructions are loaded into memory accessible by atleast one computer processor (for example, a programmable microprocessoror microcontroller or an application specific integrated circuit). Theat least one computer processor then executes the instructions, causingcomputer hardware to perform the specific functions defined by thecomputer-executable instructions. As will be appreciated by a person ofordinary skill in the art, computer execution of computer-executableinstructions is equivalent to the performance of the same functions byelectronic hardware that includes hardware circuits that are hardwiredto perform the specific functions. As such, while embodimentsillustrated herein are typically implemented as some combination ofcomputer hardware and computer-executable instructions, the embodimentsillustrated herein could also be implemented as one or more electroniccircuits hardwired to perform the specific functions illustrated herein.

The various systems, devices and/or related methods disclosed herein canbe used to at least partially ablate and/or otherwise ablate, heat orotherwise thermally treat one or more portions of a subject's anatomy,including without limitation, cardiac tissue (e.g., myocardium, atrialtissue, ventricular tissue, valves, etc.), a bodily lumen (e.g., vein,artery, airway, esophagus or other digestive tract lumen, urethra and/orother urinary tract vessels or lumens, other lumens, etc.), sphincters,prostate, brain, gall bladder, uterus, other organs, tumors and/or othergrowths, nerve tissue and/or any other portion of the anatomy. Theselective ablation and/or other heating of such anatomical locations canbe used to treat one or more diseases or conditions, including, forexample, atrial fibrillation (persistent or paraoxysmal), atrialflutter, ventricular tachycardia, mitral valve regurgitation, othercardiac diseases, asthma, chronic obstructive pulmonary disease (COPD),other pulmonary or respiratory diseases, including benign or cancerouslung nodules, hypertension, heart failure, denervation, renal failure,obesity, diabetes, gastroesophageal reflux disease (GERD), othergastroenterological disorders, other nerve-related disease, tumors orother growths, pain and/or any other disease, condition or ailment.

In any of the embodiments disclosed herein, one or more components,including a processor, computer-readable medium or other memory,controllers (e.g., dials, switches, knobs, etc.), contact sensingsubsystem, displays (e.g., temperature displays, timers, etc.) and/orthe like are incorporated into and/or coupled with (e.g., reversibly orirreversibly) one or more modules of the generator, the irrigationsystem (e.g., irrigant pump, reservoir, etc.) and/or any other portionof an ablation or other modulation or treatment system.

Although several embodiments and examples are disclosed herein, thepresent application extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses of theinventions and modifications and equivalents thereof. It is alsocontemplated that various combinations or subcombinations of thespecific features and aspects of the embodiments may be made and stillfall within the scope of the inventions. Accordingly, it should beunderstood that various features and aspects of the disclosedembodiments can be combine with or substituted for one another in orderto form varying modes of the disclosed inventions. The headings usedherein are merely provided to enhance readability and are not intendedto limit the scope of the embodiments disclosed in a particular sectionto the features or elements disclosed in that section.

While the embodiments disclosed herein are susceptible to variousmodifications, and alternative forms, specific examples thereof havebeen shown in the drawings and are herein described in detail. It shouldbe understood, however, that the inventions are not to be limited to theparticular forms or methods disclosed, but, to the contrary, theinventions are to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the various embodiments describedand the appended claims. Any methods disclosed herein need not beperformed in the order recited. The methods disclosed herein includecertain actions taken by a practitioner; however, they can also includeany third-party instruction of those actions, either expressly or byimplication. For example, actions such as “advancing a catheter” or“delivering energy to an ablation member” include “instructing advancinga catheter” or “instructing delivering energy to an ablation member,”respectively. The ranges disclosed herein also encompass any and alloverlap, sub-ranges, and combinations thereof. Language such as “up to,”“at least,” “greater than,” “less than,” “between,” and the likeincludes the number recited. Numbers preceded by a term such as “about”or “approximately” include the recited numbers. For example, “about 10mm” includes “10 mm.” Terms or phrases preceded by a term such as“substantially” include the recited term or phrase. For example,“substantially parallel” includes “parallel.”

What is claimed is:
 1. A method of determining an orientation of adistal end of an ablation catheter with respect to a target region, themethod comprising: receiving signals indicative of temperature from aplurality of temperature sensors distributed along a distal end of anablation catheter at a first plurality of time points in a first periodof time; determining temperature measurement values at each of the firstplurality of time points for each of the plurality of temperaturesensors; calculating a starting temperature value for each of theplurality of temperature sensors based on the determined temperaturemeasurement values; receiving signals indicative of temperature from theplurality of temperature sensors at a second plurality of time points ina second period of time after the first period of time; determiningtemperature measurement values at each of the second plurality of timepoints for each of the plurality of temperature sensors; calculating arate of change between the determined temperature values at each of thesecond plurality of time points and a starting temperature value foreach of the plurality of temperature sensors; and at each time point ofthe second plurality of time points, determining an orientation of thedistal end of the ablation catheter relative to a target surface basedon a comparison of the calculated rate of change of at least two of theplurality of temperature sensors.
 2. The method of claim 1: wherein theplurality of temperature sensors comprises a first plurality oftemperature sensors positioned at a distal tip of the ablation catheterand a second plurality of temperature sensors positioned at a distanceproximal to the first plurality of temperature sensors, wherein thefirst plurality of temperature sensors consists of a first threethermocouples spaced apart circumferentially about a longitudinal axisof the ablation catheter, wherein the second plurality of temperaturesensors consists of a second three thermocouples spaced apartcircumferentially about the longitudinal axis of the ablation catheter,wherein the distal end of the ablation catheter further comprises atleast one thermal shunt member in thermal communication with the atleast one energy delivery member and at least one fluid conduitextending at least partially through an interior of the elongate body,wherein the at least one thermal shunt member is in thermalcommunication with the at least one fluid conduit, and wherein the stepof determining an orientation of the distal end of the ablation catheterrelative to a target surface comprises determining an initialorientation in less than 5 seconds after application of ablative energyby an energy source coupled to the ablation catheter.
 3. The method ofclaim 1, wherein calculating the starting temperature value for each ofthe plurality of temperature sensors comprises averaging the temperaturemeasurement values determined at each of the first plurality of timepoints.
 4. The method of claim 1, wherein the plurality of temperaturesensors comprises a first plurality of temperature sensors positioned ata distal tip of the ablation catheter and a second plurality oftemperature sensors positioned at a distance proximal to the firstplurality of temperature sensors.
 5. The method of claim 1, whereindetermining the orientation of the distal end of the ablation catheterrelative to the target surface based on a comparison of the calculatedrates of change of at least two of the plurality of temperature sensorscomprises determining whether the calculated rates of change satisfy oneor more orientation criteria of a respective orientation.
 6. The methodof claim 5, wherein the orientation is determined from one of aplurality of orientation options and wherein the orientation criteriaare different for each of the orientation options.
 7. The method ofclaim 5, wherein at least some of the orientation criteria aretime-dependent.
 8. The method of claim 5, wherein the orientationcriteria are empirically determined.
 9. A method of determining anorientation of a distal end of an ablation catheter with respect to atarget region, the method comprising: receiving signals indicative oftemperature from a plurality of temperature sensors distributed along adistal end of an ablation catheter at a plurality of time points over aperiod of time; determining temperature measurement values at each ofthe plurality of time points for each of the plurality of temperaturesensors; calculating a rate of change between the determined temperaturevalues at each of the plurality of time points and a startingtemperature value for each of the plurality of temperature sensors; ateach time point of the plurality of time points, determining anorientation of the distal end of the ablation catheter relative to atarget surface based on a comparison of the calculated rate of change ofat least two of the plurality of temperature sensors.
 10. The method ofclaim 9, wherein the plurality of time points each occur after deliveryof ablative energy has been initiated by the ablation catheter.
 11. Themethod of claim 9, wherein the step of determining the orientation ofthe distal end of the ablation catheter comprises determining an initialorientation in less than 5 seconds after application of ablative energyby an energy source coupled to the ablation catheter.
 12. The method ofclaim 9, wherein the plurality of temperature sensors comprises a firstplurality of temperature sensors positioned at a distal tip of theablation catheter and a second plurality of temperature sensorspositioned at a distance proximal to the first plurality of temperaturesensors.
 13. The method of claim 9, wherein determining the orientationof the distal end of the ablation catheter relative to the targetsurface based on a comparison of the calculated rates of change of atleast two of the plurality of temperature sensors comprises determiningwhether the calculated rates of change satisfy one or more orientationcriteria of a respective orientation.
 14. The method of claim 13,wherein the orientation is determined from one of a plurality oforientation options and wherein the orientation criteria are differentfor each of the orientation options.
 15. The method of claim 13, whereinat least some of the orientation criteria are time-dependent.
 16. Amethod of determining an orientation of a distal end of an ablationcatheter with respect to a target region, the method comprising:receiving signals indicative of temperature from a plurality oftemperature sensors distributed along a distal end of an ablationcatheter at a plurality of time points over a period of time;determining temperature measurement values at each of the plurality oftime points for each of the plurality of temperature sensors;determining a characteristic of a temperature response at each of theplurality of time points for each of the plurality of temperaturesensors; at each time point of the plurality of time points, determiningan orientation of the distal end of the ablation catheter relative to atarget surface based on a comparison of the characteristics of thetemperature responses of at least two of the plurality of temperaturesensors.
 17. The method of claim 16, wherein the characteristic of thetemperature response is a rate of change of the temperature response.18. The method of claim 16, wherein the plurality of temperature sensorscomprises a first plurality of temperature sensors positioned at adistal tip of the ablation catheter and a second plurality oftemperature sensors positioned at a distance proximal to the firstplurality of temperature sensors.
 19. The method of claim 16, whereindetermining the orientation of the distal end of the ablation catheterrelative to the target surface based on characteristics of thetemperature responses of at least two of the plurality of temperaturesensors comprises determining whether the characteristics of thetemperature responses satisfy one or more orientation criteria of arespective orientation.
 20. The method of claim 19, wherein theorientation is determined from one of a plurality of orientation optionsand wherein the orientation criteria are different for each of theorientation options.